First simple version for comparing two PBLs.
Move multiple PBIs in one operation.
Implement strategy for finding moves from between two PBLs.
Merge branch 'master' of
https://github.com/FrankBeeh/ProductBacklogTimeline.git

Conflicts:
	ProductBacklog/src/main/de/frankbeeh/productbacklogtimeline/data/ProductBacklogChange.java
	ProductBacklog/src/main/de/frankbeeh/productbacklogtimeline/service/diff/ProductBacklogDiff.java
	ProductBacklog/src/test/de/frankbeeh/productbacklogtimeline/service/diff/ProductBacklogDiffTest.java