Docker mix and match setup

Rewrite of the docker setup. Now uses fig to manage containers and container
linkage. The base is a block based mix and match, which will give you the
possibility to easily test all configurations.

docker/blocks/w_db_cache/fig

@@ -0,0 +1,7 @@
+gogs:
+  build: docker
+  links:
+    - db
+    - cache
+  ports:
+    - "3000:3000"