Stash a serialized version of items being updated or deleted into
the system event node, which should work as a poor-man's version
of versioning.
Merge branch 'master' into serialized_versions

Conflicts:
	ehri-frames/src/main/java/eu/ehri/project/views/impl/LoggingCrudViews.java
DO NOT cache count on fetch because we probably aren't in a TX
Add a version node type which holds a serialized version of an item
being updated or deleted. This is created by the ActionManager, and
connected to the event which triggers the change.

Also optimised imports.