add lint.xml files to Android project folders

in order to be able to check lint warnings with our config,
lint.xml files are introduced with ignored checks.
- add lint.xml files (they were located in our jenkins repo)
- remove them from .gitignore
- move ignore logic in testprojects from Manifest to lint.xml
- comment tools:ignore in .xml files
- ignore NewApi warning for textAllCaps - is just capitalized
on Android 2.3.x
- ignore Icon Density warning - icons will be provided by UI team,
and warning will be activated again
Merge pull request #672 from Catrobat/introduceLint

introduce lint