Add fig.yml support

Implementing #152

I added on current fig.yml `latest` container tag which is used on development also. I think it's the most appropriate in order to work for both development & production-like environments.

Though this doesn't trigger docker build automagically, `make build` needs to be executed previously on development. Alternatively fig.yml `image` tag could be replaced with `build`, though then it will not work remotely.

In order to implement the database initialization on startup, I had to update the assets/init script to the following:

- decoupled database creation with DB_INIT flag activation and activated the check for both localhost & remote mysql database instances (no postgres since fig.yml supports mysql only)

It is tested with following commands:

<pre>
make purge build quickstart logs
</pre>

<pre>
fig rm --force
fig up # First time launch, database is initialized
fig up # second time launch, database is left untouched
</pre>