Implemented PropertyRelations service.

Summary:
Signed-off-by: Ralf Floca <r.floca@dkfz-heidelberg.de>

Implemented test for property relations service

Signed-off-by: Ralf Floca <r.floca@dkfz-heidelberg.de>

Added property relations service to core activator and services

Signed-off-by: Ralf Floca <r.floca@dkfz-heidelberg.de>

removed dublicate line.

Signed-off-by: Ralf Floca <r.floca@dkfz-heidelberg.de>

removed unnecessary includes.

Signed-off-by: Ralf Floca <r.floca@dkfz-heidelberg.de>

Test Plan: unit tests

Reviewers: O1 MITK Core!

Maniphest Tasks: T23766

Differential Revision: https://phabricator.mitk.org/D97