Upgrades geonode to upstream 4.2.1

[ridoo]

Upgrades geonode and each dependent component to upstream version 4.2.0 by keeping thuenen adjustments. Will have to make more test. Findings/necessary changes include:

• Align with upstream version
  • geonode-mapstore-client
  • MapStore2
  • GeoNode
  • Thuenen_atlas
• Notable configuration changes
  • INVOKE_LOG_STDOUT became reasonable default (removed our setting)
  • geoserver credentials can be set initially via GEOSERVER_FACTORY_PASSWORD and GEOSERVER_ADMIN_PASSWORD (or re-do via FORCE_REINIT with respect to the currently set password)
  • OAUTH2_CLIENT_ID and OAUTH2_CLIENT_SECRET now have to be set explicitly in the dev-environment

:warning: Database from migration has to be done first! Details have to be determined -- most probably, a dump/backup and restore, similar to this:

docker-compose exec db pg_dumpall -c -U geonode > db_13_dump.sql
cat db_13_dump.sql | sudo docker-compose exec -T db_15 psql -U geonode

Resolves: #17

[ridoo]

GeoSolutions has release v4.2.1 already with minor changes. Will update this PR soon