[508294] ResourceAttachmentChange is displayed twice

With the new way to display differences and matches in the structure
merge viewer, the ResourceAttachmentChanges were displayed twice in each
GroupProvider (ThreeWayGroupProvider, DefaultGroupProvider,
ResourceGroupProvider, KindGroupProvider).

Change-Id: I0c659b832fb32aa2f29f9722e61601c46a7c77d2
Signed-off-by: Axel Richard <axel.richard@obeo.fr>
12 files changed