POC: Introduce Nextcloud based on Nginx web server.

UPDATE:
 - stack.yml contains FPM & Mariadb containers, updated names and hostnames for container
TODO:
 - update config.ini for trusted proxies support

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    + '--link' option for docker create is obsolete and we need communication between fpm and nginx container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

Signed-off-by: Malanik Jan <malanik.jan@gmail.com>

stack.yml

@@ -2,30 +2,44 @@ version: '3.2'
 
 services:
   db:
-    image: postgres
+    name: mariadb
+    hostname: db
+    image: mariadb
+    tag: 10.4.4-bionic
     restart: always
     volumes:
-      - db:/var/lib/postgresql/data
+      - db:/var/lib/mysql
     environment:
-      - POSTGRES_DB=nextcloud
-      - POSTGRES_USER=nextcloud
-      - POSTGRES_PASSWORD=nextcloud
-
+      - MYSQL_ROOT_PASSWORD=mariadb_admin
+      - MYSQL_DATABASE=nextcloud
+      - MYSQL_USER=nextcloud_admin
+      - MYSQL_PASSWORD=nextcloud_admin
+  fpm:
+    name: fpm
+    hostname: fpm 
+    image: 1john2ci/nextcloud
+    tag: 16.0-fpm-full
+    restart: always
+    volumes:
+      - nextcloud:/var/www/html
   app:
-    image: nextcloud
+    name: nextcloud
+    hostname: nextcloud
+    image: 1john2ci/nextcloud
+    tag: 16.0-nginx
     restart: always
     ports:
-      - 8080:80
+      - 127.0.0.1:8080:80
     volumes:
       - nextcloud:/var/www/html
     environment:
-      - POSTGRES_HOST=db
-      - POSTGRES_DB=nextcloud
-      - POSTGRES_USER=nextcloud
-      - POSTGRES_PASSWORD=nextcloud
+      - MYSQL_DATABASE=nextcloud
+      - MYSQL_USER=nextcloud_admin
+      - MYSQL_PASSWORD=nextcloud_admin
+      - MYSQL_HOST=db
     depends_on:
       - db
-
+      - fpm
   cron:
     image: nextcloud
     restart: always
@@ -36,5 +50,5 @@ services:
       - db
 
 volumes:
-  db:
-  nextcloud:
+  db: /srv/mariadb
+  nextcloud: /srv/nextcloud