Fix for issue #585 "Don't log in release builds."

DO NOT MERGE. @stypen found a much easier solution: https://github.com/Catrobat/Catroid/issues/585#issuecomment-22468088

Log messages are disabled for releases but can be activated in the preferences.
Log messages should be sent using the org.catrobat.catroid.utils.Logger class now. (Can be used like android.util.Log)

(The order of some imports has changed when I used the Optimize imports feature of Android Studio.)