Initial work on virtual collection creation.

 - currently based on doc unit views
 - no i18n messages yet
 - doesn't allow actually linking descriptions yet
More copy-pasta allowing VUs to create virtual descriptions
Move VU controller/views to archdesc module, add search
Experimenting with logging
Tweaks to language rendering
Various small issues with virtual units
Merge branch 'virtual_units' of github.com:mikesname/docview into virtual_units
Merge branch 'master' into virtual_units

Conflicts:
	modules/core/app/models/DocumentaryUnit.scala
	modules/core/app/views/Helpers.scala
Merge branch 'master' into virtual_units

Conflicts:
	modules/archdesc/app/views/documentaryUnit/show.scala.html
Update dubious compat server runner for Neo4j 1.9.7
Refactoring and cleanup of JSON parsing stuff.
 - make equalsReads and nullableListReads/Writes/Format a method on
   a JsPath extension class (looks neater and more consistent)
 - various formatting cleanups and reindentation
 - fix reading of virtual unit description references
More clean up of JSON reads
More JSON cleanup and refactoring
Add note to docs about  extensions
Fix typo in class name
Don't show data policy widget to logged-in users
Upgrade to Play 2.2.3, update some deps, remove unused Gremlin stuff
Merge branch 'master' into play-2.3rc1

Conflicts:
	modules/core/app/backend/rest/gremlin/GremlinDAO.scala
	modules/core/app/controllers/generic/Read.scala
	project/Build.scala
	project/plugins.sbt