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    + '--link' option for docker create is obsolete and we need communication between fpm and nginx container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: https://travis-ci.org/1john2/docker/builds/530329740

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

15.0/fpm/Dockerfile

@@ -1,139 +0,0 @@
-# DO NOT EDIT: created by update.sh from Dockerfile-debian.template
-FROM php:7.3-fpm-stretch
-
-# 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-3.4.3; \
-    \
-    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 15.0.7
-
-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/
-
-ENTRYPOINT ["/entrypoint.sh"]
-CMD ["php-fpm"]