Fix some lint warnings

see commit messages for more Information!
additionally auto-formatted all modified .xml files in res-folder.

master branch with current lint.xml Config: http://jenkins.catrob.at/job/Catroid-Code-Checker/28/
this branch with current lint.xml Config: http://jenkins.catrob.at/job/Catroid-Code-Checker/29/

current lint.xml is located here: https://github.com/Catrobat/Jenkins/blob/master/customScripts/lint.xml#
all other rules were not touched (default lint rules - Android SDK 22.0.5)

multijob run: http://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/95/
single emulator tests of "yellow" tests:
http://jenkins.catrob.at/view/Catroid/job/Catroid-single-UI-emulator/80/console
http://jenkins.catrob.at/view/Catroid/job/Catroid-single-UI-emulator/83/console