feat: support running using Docker Compose

This commit adds a Docker Compose file which will run the application
using docker. The application is fronted by Traefik, and runs using
PHP-fpm. nginx is used to accept queries from Traefik and relay them to
the PHP-fpm containers (Traefik doesn't support FastCGI directly).
Sessions are shared between the various PHP containers using memcached.

Part of this work is based on [this repo](https://github.com/wandersonwhcr/docker-nginx-php-fpm)

docker/nginx-templates/default.conf.template

@@ -0,0 +1,21 @@
+server {
+    listen 80;
+
+    index index.php;
+    root /var/www/tasks/site;
+
+    location / {
+    	try_files $uri /index.php$request_uri;
+	
+    }
+
+    location /index.php/ {
+        fastcgi_pass application:9000;
+
+	fastcgi_split_path_info ^(.+?\.php)(/.*)$;
+        include fastcgi_params;
+	fastcgi_param PATH_INFO       $fastcgi_path_info;
+	fastcgi_param SCRIPT_NAME     "/index.php";
+	fastcgi_param SCRIPT_FILENAME $document_root/index.php;
+    }
+}