Merge pull request #207 from Catrobat/bgColorIssue

The image Caching could be further improved : At the moment we have redundant code whenever an image is not in the cache, we have to manually load it into the cache (each class has the same code))
Merge pull request #208 from Catrobat/issue#203

fixes #203
fixes #210 - correct launch image
fixes #211, wrong status bar color on launch
Merge branch 'master' of github.com:Catrobat/Catty into development
Merge branch 'launch-image' into development