Merge branch 'release/2.3.1'

de.prob.ui/META-INF/MANIFEST.MF

de.prob.ui/icons/print.png

de.prob.ui/icons/zoom_in.png

de.prob.ui/icons/zoom_out.png

de.prob.ui/plugin.xml

de.prob.ui/src/de/prob/ui/StateBasedViewPart.java

...b.ui/src/de/prob/ui/historyview/HistoryLabelProvider.java

de.prob.ui/src/de/prob/ui/historyview/HistoryView.java

...c/de/prob/ui/invcheck/InvariantCheckFinishedListener.java

...rob.ui/src/de/prob/ui/ltl/CounterExampleBinaryFigure.java

de.prob.ui/src/de/prob/ui/ltl/CounterExampleComposite.java

de.prob.ui/src/de/prob/ui/ltl/CounterExampleEditPart.java

de.prob.ui/src/de/prob/ui/ltl/CounterExampleFigure.java

...b.ui/src/de/prob/ui/ltl/CounterExampleHistoryHandler.java

...b.ui/src/de/prob/ui/ltl/CounterExampleLoadedProvider.java

...rob.ui/src/de/prob/ui/ltl/CounterExampleMouseAdapter.java

....ui/src/de/prob/ui/ltl/CounterExamplePredicateFigure.java

...rob.ui/src/de/prob/ui/ltl/CounterExamplePrintHandler.java

...src/de/prob/ui/ltl/CounterExamplePropositionEditPart.java

...i/src/de/prob/ui/ltl/CounterExamplePropositionFigure.java