Rationale:

• avoid having two versions of Nginx and Letsencrypt dockerfiles both in geonode and geonode-project
• avoid a mix of separate repos for docker images (postgis, geoserver. nginx, etc.) and in geonode and/or geonode-project. Keppeing them aligned is a mess
• geonode-project is meant for customized versions of GeoNode, so having the ability to build custom images for the services fits well here
• by default both geonode and geonode-project will use the published images