Implementation of contextual tooltips

1) add tooltips for CHANGE, ADD, DELETE, MOVE actions
2) add default implementation
3) add basic implementation for uml and diagram diffs
4) add unit tests

Change-Id: I9cbfa42ca256b94a1a5d530d13d993170a67073a
Signed-off-by: Mathieu Cartaud <mathieu.cartaud@obeo.fr>

111 files changed