bottom bar redesigned
added pngs
added mdpi images
testcase + bugfix
applied bottom bar style to actionbar
Merge pull request #185 from Catrobat/Issue#184

Fixed Issue #184
Merge pull request #187 from Catrobat/BottomBarRedesign

Issue #183: Bottom bar redesigned
Merge branch 'master' into MainMenuActivityLayoutFinetuning
refactoring MainMenuActivity

* remove teststyle bold
* remove background pattern