[443337] Prevent large shapes icons for stereotypes.

Papyrus also uses UML icons to define shapes to be used in diagrams.
Those shapes should not be used in the structure merge viewer.

Bug: 443337
Change-Id: I1fade6cd71c90bfbff04340d712898343d7dbdf5
Prevents loading twice the same model in a NotLoadingResourceSet.

The previsous getResource(IStorage,boolean) method did not check if a
resource was already loaded. It may happen that the same resource was
created twice in the same ResourceSet (with the exact same uri).

This commit also changes the way IStorage are loaded in the resource
set. The IStorages are now loaded using their uris. The resource set is
aware of the resources that should be loaded from a IStorage. 

Change-Id: I5fe2f837c7a0c3ff522ee3d382e4b3dc7fc4b9d9
Signed-off-by: Arthur Daussy <arthur.daussy@obeo.fr>
Adds ResourceSetHook extension point.


This extension point aims to provide a way for external client to hook
some behavior into the ResourceSet used by EMF Compare (for example
register new factories).


Change-Id: I9273648a9bcbca8da6e1a7dbb41870c94f20ac07
[398367] Adds Papyrus CSS customization support.

This adds a hook on EMF Compare resource set in order install all
necessary stuff to support Papyrus CSS support in EMF Compare.

Bug: 398367
Change-Id: I1eb74520698e6160a2d779dedd5cb088d85828dc