Changed buildtools version and target sdk version in build.gradle

Also some coding style edits(now using android studio auto format for .gradle files)

Also, there is a new version of the android gradle plugin (0.7) for Gradle 1.9.
But this version is still buggy so it is not yet included in this PR.

Jenkins build: https://jenkins.catrob.at/job/Catroid-Multi-Job-Custom-Branch/911/