fix some lint warnings

- remove unused resources
- add @TargetApi in UiTestUtils - android.R.id.home needs minSdk 11;
  we have set 10 in our manifest; but the code is only executed if
  version is at least 4.0.3, so warning can be supressed
- fish.jpg IS a .png file
- menu_script.xml unused due to recent changes
Merge pull request #564 from Catrobat/fixLintWarnings

Fix of some lint warnings