POC: Introduce Nextcloud based on Nginx web server.

This PR introduce POC of Nextcloud based on Nginx web server with php-fpm in separated container.
Basic installation with SQLite and few operations in web gui were tested.

Nginx dockerfile is generated from Dockerfile-nginx.template
  - FROM string has hardcoded variant - apache
  - There is no upstream PHP image with Nginx, due this generate-stackbrew-library is not able to identify parent correctly

New files were introduced in image:
  - Dockerfile-nginx.template
  - nginx-foreground
    + simulates behavior of apache2-foreground cmd
  - 16.0/nginx/Dockerfile
    + generated from template Dockerfile-nginx.template
  - nextcloud.confx
    + Nginx vhost configuration
  - start_net.sh (temporary)
    + Helper script to create user-defined network for Docker
    + '--link' option for docker create is obsolete and we need communication between fpm and nginx container
  - start_container.sh (temporary)
    + Helper script to handle containers
  - Dockerfile
    + /Dockerfile for verification purposes
Updated files:
  - set -x added to all shell scripts for easier troubleshooting (temporary)
  - update.sh
    + New variant introduced
    + Number of builded variant is limited for simplified CI.
  - .travis.yml (temporary)
    + Image push to registry for testing purposes
  - docker-entrypoint.sh
    + Recognizes new argument for entrypoint - nginx-foreground

Be careful during review, github recognizes removed files for 15.0 release as renamed to 16.0/nginx variant

Motivation/Usecase:
  - I have openvz based VPS where only old Docker 1.10 is supported.
  - Apache(in nextcloud container) in combination Nginx as a reverse proxy for multiple vhosts doesn't work correctly

Image pull link:
docker pull 1john2ci/nextcloud:apache-20190509
docker pull 1john2ci/nextcloud:fpm-20190509
Travis CI test: 530329740

Deployment notes:
  - Clone source code
  - Create user-defined network for Docker
  - Start fpm container
  - Start nginx container

16.0/nginx/Dockerfile

@@ -0,0 +1,187 @@
+# DO NOT EDIT: created by update.sh from Dockerfile-nginx.template
+FROM php:7.3-apache-stretch
+
+# ##
+# It's bad idea to use FROM nginx:latest, we will not be aligned
+# We can't use 7.3-nginx-stretch - it's not valid PHP upstream image
+# Tricky part....
+# I have to figure out howto handle it
+# Error message from generate-stackbrew-library: tag not found in manifest for "php": "7.3-nginx-stretch"
+# Potential solution: Custom tag in dockerfile template replaced with Nginx stuff
+# ##
+
+# ##
+# Install Nginx & standard troubleshooting utils
+# We can't remove apache2 - it brokes build for fpm/apache containers
+# ##
+RUN set -ex; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        nginx \
+        vim \
+        net-tools \
+        iproute2 \
+        iputils-ping \
+        wget \
+        psmisc \
+        procps \
+    ; \
+    rm -rf /var/lib/apt/lists/*;
+# entrypoint.sh and cron.sh dependencies
+RUN set -ex; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        rsync \
+        bzip2 \
+        busybox-static \
+    ; \
+    rm -rf /var/lib/apt/lists/*; \
+    \
+    mkdir -p /var/spool/cron/crontabs; \
+    echo '*/15 * * * * php -f /var/www/html/cron.php' > /var/spool/cron/crontabs/www-data
+
+# install the PHP extensions we need
+# see https://docs.nextcloud.com/server/stable/admin_manual/installation/source_installation.html
+RUN set -ex; \
+    \
+    savedAptMark="$(apt-mark showmanual)"; \
+    \
+    apt-get update; \
+    apt-get install -y --no-install-recommends \
+        libcurl4-openssl-dev \
+        libevent-dev \
+        libfreetype6-dev \
+        libicu-dev \
+        libjpeg-dev \
+        libldap2-dev \
+        libmcrypt-dev \
+        libmemcached-dev \
+        libpng-dev \
+        libpq-dev \
+        libxml2-dev \
+        libmagickwand-dev \
+        libzip-dev \
+    ; \
+    \
+    debMultiarch="$(dpkg-architecture --query DEB_BUILD_MULTIARCH)"; \
+    docker-php-ext-configure gd --with-freetype-dir=/usr --with-png-dir=/usr --with-jpeg-dir=/usr; \
+    docker-php-ext-configure ldap --with-libdir="lib/$debMultiarch"; \
+    docker-php-ext-install \
+        exif \
+        gd \
+        intl \
+        ldap \
+        opcache \
+        pcntl \
+        pdo_mysql \
+        pdo_pgsql \
+        zip \
+    ; \
+    \
+# pecl will claim success even if one install fails, so we need to perform each install separately
+    pecl install APCu-5.1.17; \
+    pecl install memcached-3.1.3; \
+    pecl install redis-4.3.0; \
+    pecl install imagick-3.4.4; \
+    \
+    docker-php-ext-enable \
+        apcu \
+        memcached \
+        redis \
+        imagick \
+    ; \
+    \
+# reset apt-mark's "manual" list so that "purge --auto-remove" will remove all build dependencies
+    apt-mark auto '.*' > /dev/null; \
+    apt-mark manual $savedAptMark; \
+    ldd "$(php -r 'echo ini_get("extension_dir");')"/*.so \
+        | awk '/=>/ { print $3 }' \
+        | sort -u \
+        | xargs -r dpkg-query -S \
+        | cut -d: -f1 \
+        | sort -u \
+        | xargs -rt apt-mark manual; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false; \
+    rm -rf /var/lib/apt/lists/*
+
+# set recommended PHP.ini settings
+# see https://docs.nextcloud.com/server/12/admin_manual/configuration_server/server_tuning.html#enable-php-opcache
+RUN { \
+        echo 'opcache.enable=1'; \
+        echo 'opcache.enable_cli=1'; \
+        echo 'opcache.interned_strings_buffer=8'; \
+        echo 'opcache.max_accelerated_files=10000'; \
+        echo 'opcache.memory_consumption=128'; \
+        echo 'opcache.save_comments=1'; \
+        echo 'opcache.revalidate_freq=1'; \
+    } > /usr/local/etc/php/conf.d/opcache-recommended.ini; \
+    \
+    echo 'apc.enable_cli=1' >> /usr/local/etc/php/conf.d/docker-php-ext-apcu.ini; \
+    \
+    echo 'memory_limit=512M' > /usr/local/etc/php/conf.d/memory-limit.ini; \
+    \
+    mkdir /var/www/data; \
+    chown -R www-data:root /var/www; \
+    chmod -R g=u /var/www
+
+VOLUME /var/www/html
+
+
+ENV NEXTCLOUD_VERSION 16.0.0
+
+RUN set -ex; \
+    fetchDeps=" \
+        gnupg \
+        dirmngr \
+    "; \
+    apt-get update; \
+    apt-get install -y --no-install-recommends $fetchDeps; \
+    \
+    curl -fsSL -o nextcloud.tar.bz2 \
+        "https://download.nextcloud.com/server/releases/nextcloud-${NEXTCLOUD_VERSION}.tar.bz2"; \
+    curl -fsSL -o nextcloud.tar.bz2.asc \
+        "https://download.nextcloud.com/server/releases/nextcloud-${NEXTCLOUD_VERSION}.tar.bz2.asc"; \
+    export GNUPGHOME="$(mktemp -d)"; \
+# gpg key from https://nextcloud.com/nextcloud.asc
+    gpg --batch --keyserver ha.pool.sks-keyservers.net --recv-keys 28806A878AE423A28372792ED75899B9A724937A; \
+    gpg --batch --verify nextcloud.tar.bz2.asc nextcloud.tar.bz2; \
+    tar -xjf nextcloud.tar.bz2 -C /usr/src/; \
+    gpgconf --kill all; \
+    rm -r "$GNUPGHOME" nextcloud.tar.bz2.asc nextcloud.tar.bz2; \
+    rm -rf /usr/src/nextcloud/updater; \
+    mkdir -p /usr/src/nextcloud/data; \
+    mkdir -p /usr/src/nextcloud/custom_apps; \
+    chmod +x /usr/src/nextcloud/occ; \
+    \
+    apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false $fetchDeps; \
+    rm -rf /var/lib/apt/lists/*
+
+COPY *.sh upgrade.exclude /
+COPY config/* /usr/src/nextcloud/config/
+
+# ##
+# Remove Nginx default website and add support for php
+# ##
+RUN set -ex; \
+\
+  rm /etc/nginx/sites-enabled/default; \
+  sed -i '/types {/a\ \ \ \ application\/x-httpd-php\t\tphp;' '/etc/nginx/mime.types';
+
+# ##
+# COPY Nextcloud vhost cfg for Nginx
+# ##
+COPY nextcloud.conf /etc/nginx/conf.d/
+# ##
+# COPY new entrypoint for nginx
+# ##
+COPY nginx-foreground /usr/local/bin/
+# ##
+# COPY Dockerfile for verification purposes
+# ##
+COPY Dockerfile /
+
+ENTRYPOINT ["/entrypoint.sh"]
+CMD ["nginx-foreground"]