Proposal: refactored metadata editor UI for 2.12

[lushc]

https://github.com/geonetwork/core-geonetwork/wiki/Refactoring-editor

A proposal has been made to refactor the editor UI (and general UI I believe) and is targetted for the 2.12 release. A new version of the schema plugin may have to be written to support the new metadata editor, although how significant the changes needed are is not yet clear. Interestingly there may be scope to move the integration of the GEO label away from the plugin itself and into a widget if they will be depending on such widgets for things like bounding box.

Not much to do but continue to track the progress of this proposal for now.