First implementation of ImageToImageRelationRule

Summary:
Tests are missing

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

Added unit tests for SourceImageRelationRule.

Open todo: check gcc/clang

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

Test Plan: unit test "SourceImageRelationRuleTest"

Reviewers: MITK Reviewer Group I, kislinsk

Reviewed By: MITK Reviewer Group I, kislinsk

Subscribers: kislinsk

Maniphest Tasks: T23808

Differential Revision: https://phabricator.mitk.org/D195