Java 11 build using latest GeoTools (and include geosolutions/mapfish-print improvements for GeoNode community)

[jodygarnett]

This is being used to test https://github.com/geotools/geotools/pull/4367 and will be submitted for review and release as 2.3.0 when completed.

The PR includes update instructions (in the docs) providing some guidance for both 2.2.0 users, and geosolutions/mapfish-print users migrating to a common codebase.

There is considerable new functionality and bugs fixed on both sides making integration testing advisable.

See also:

• https://github.com/mapfish/mapfish-print-v2/issues/11
• https://github.com/geosolutions-it/mapfish-print/issues/65

[jodygarnett]

This branch is working, I wish to confirm it can deploy to OSGeo repository before continuing.