[456699] Add Model Resolving Integration Extension Point

Adds an extension point to EMF Compare which allows to integrate special
model resolving behavior into EMF Compare. The extension point can be
used when dependencies between resources exist by design but do not
manifest in the resources themselves.

The extension point is used for integrating the Papyrus ModelSet
approach where the .di file is used as "master" file without actually
linking to other files.

Includes testcases.

Bug: 456699
Also-by: Philip Langer <planger@eclipsesource.com>
Signed-off-by: Stefan Dirix <sdirix@eclipsesource.com>
Change-Id: Ia0104462a5f2737c8890d92a9e94ab8675db2773
20 files changed