Define docker-compose and related services images

[giohappy]

Docker compose (version==2) with the following features:

• A volume for Geoserver's DATA_DIR, available both to Geoserver and GeoNode
• A volume for GeoNode's MEDIA and STATIC files
• A volume for backups

[cezio]

should we also enable:

• celery
• rabbitmq
• elasticsearch
• consumers

containers?

[giohappy]

I would leave them out for the moment. For celery, rabbitmq and consumers:

• by default tasks are run sync and locally. See this default setting. We will do some more testing on making things async, but for the moment I qould keep things simple, given the kind of "automated" deployment. If we employ celery workers a supervisor should be installed and configured to monitor workers, etc. Too many volatile things in this moment...
• the same for messaging. If a broker is not defined eveything is managed locally and sync