Additional unit test for merge

Add a unit test to OverlappingMergeTest for:

A: A,B,C
B: A,B,C
C: A,B,C

Then, the following view is installed:

A: A,B
B: A,B
C: A,B,C // still has the same view

Make sure that a merge ensues which installs view A,B,C in all 3 members