Improve final state and MergeData when merging

Mergers now properly set the final state of diffs according to whether
they were accepted or rejected.
We now install a DiffStateAdapter on the comparison and all its diffs to
listen to diff state changes and update MergeData accordingly.

Change-Id: Ib0945557e4a90feab82280a773ab49237e31c0ce
Signed-off-by: Laurent Delaigue <laurent.delaigue@obeo.fr>
35 files changed