[427803] Correct the reference to SiriusDiagramActionBarContributor

It has been moved to the diagram.ui plugin during the split.

Change-Id: I366cbcaa5391335c0c5c2ac459997da57eb5d49f
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[425624] Restrict Sirius Clipboard to Sirius diagrams

Sirius now provides a clipboard support poliy to provide its clipboard
support only for notation.Diagram with a DDiagram as target.

The check is done on the diagram to be able to handle the GMF Notes,
Text and Note attachments(GMF basic basic shapes available on a Sirius
Diagram).

Change-Id: Ibfa5aab70dba39b2af249bb6e90c9cb5b3ef5955
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[427803] Rename SiriusDiagramEditorPlugin into DiagramPlugin

Change-Id: Ifc0f7fdb4a0966b0be1dcee2600d1665de0b8df7
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[427803] Rename src2 into src-diag

All classes related to UI in org.eclipse.diagram have been moved to
org.eclipse.sirius.diagram.ui. 

To simplify this step almost all classes of org.eclipse.diagram have
been moved in org.eclipse.sirius.diagram.ui (and probably not only UI
classes). These classes have been moved in src-diag source folder to
facilitate future work about moving some of these classes in
org.eclipse.diagram again (See Bug 430676).


Change-Id: I8250387ea13fd031a0e79f9e993a19c023d82485
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[427803] Move DiagramPlugin in org.eclipse.sirius.diagram

DiagramPlugin has been moved to org.eclipse.sirius.diagram package, it
will be cleaned in a next step or in Bug 430676. 
Chekstyle filters have been modified to consider only src-gen package
and explicit checkstyle:off have been added on the two impacted class. 

Change-Id: I0d97db0353e5169567b26d51d10652904d721714