fix Pixel compare and screenMode test
add passepartout
improve screenshot test
fix some other pixel tests
Merge pull request #861 from Catrobat/MaximizeMode

fix issue#857: In Maximize-Mode with different screen resolutions everything around the stage should be hidden
soundproblem for android 4.4 fixed.
testcases changed to robotium 4.3.1
Merge pull request #864 from Catrobat/issue##848

soundproblem for android 4.4 hotfixed.
Merge branch 'master' into albert_robot