[457652] Give xmi:ids higher priority than attribute ids

The IdentifierEObjectMatcher will now give xmi:ids priority over
attribute ids to prevent models with duplicate xmi:ids.

Includes testcases.

Bug: 457652
Signed-off-by: Stefan Dirix <sdirix@eclipsesource.com>
Change-Id: Ia3ba4222837ecc7f6a17bccc3973ecaee334fad0
25 files changed