[427803] Fix Diagram Plugin issues

DiagramPlugin is is now a standard EMFPlugin (as SiriusPlugin,
TablePlugin, ...). 
It was previously an AbstractUIPLugin, DiagramUIPlugin is now used as
the preference store container for all diagram preferences. These
preferences still mix UI and non-UI aspects in classes from both diagram
plugins, a proper separation will be done in Bug 430676.

Bug: 427803
Change-Id: I26a7feb8e19645d00bf5f89322751be14de3d805
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[427803] Update default tools ids and paths in Environment.xmi

Pin/Unpin actions are now in the diagram.ui plugin, the id and path must
reference this plugin. 
The proper split of the file will be done in a future commit.

Change-Id: I517f859c4fddc758ee8f076c65e48542d97710e8
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[build] Update luna target after M6 release

Change-Id: Ifaa79e707b9dcd2e8a75f0bb3f4f98badc10f183
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>