Upgrade to TP 2.3.0
Implement proper ACL checks for adding/removing users from groups.

 - Also started refactoring tests to better clarity by sticking them
   in a package structure to match the eu.ehri.project package.
Merge branch 'TP-2.3.0' of github.com:mikesname/neo4j-ehri-plugin
Revert merge made while half asleep.

Revert "Merge branch 'TP-2.3.0' of github.com:mikesname/neo4j-ehri-plugin"

This reverts commit 28632aaccb7a05e25cc7c81dd474dc8df1db673f, reversing
changes made to 6e8b2eb024dbb33bae7ccd3c5f000d17051867b4.
Cleanup of models, prior to larger refactoring
Cleanup of models, prior to larger refactoring
Cleanup of models, prior to larger refactoring
More refactoring of models, aiming to reduce the responsibility of
AccessibleEntity.
Remove slashes from property names
Preparation for Tinkerpop 2.3.0 uprade. This requires reasonably big changes.
Now, all models extend a root 'Frame' interface, which itself extends
VertexFrame. This might be useful in other ways, since we can put
common methods on it, like getId and getType.
The @Property annotation on a framed interface no longer means that
that property is required. There is a new @Mandatory annotation for
denoting this.

The base class Frame now also has getId and getType methods on them,
which should enable to removal of some boilerplate elsewhere.
Add getId and getType to fake frames (anonymous accessor and system scope).
Replace some instances of manager.getId(frame) with frame.getId
More swapping of manager.getId(frame) to frame.getId()
Cleanup of imports and removal of old importer classes/tests
More cleanups
Merge branch 'master' of https://github.com/PaulBoon/neo4j-ehri-plugin
Improve still crap builddb script
Throw a runtime error if there's a missing item identifier
Merge branch 'master' of https://github.com/mikesname/neo4j-ehri-plugin

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