bug 979438 - Unify android target SDK versions r=nalexander

--HG--
rename : embedding/android/geckoview_example/AndroidManifest.xml => embedding/android/geckoview_example/AndroidManifest.xml.in
rename : mobile/android/geckoview_library/AndroidManifest.xml => mobile/android/geckoview_library/AndroidManifest.xml.in
rename : mobile/android/geckoview_library/project.properties => mobile/android/geckoview_library/project.properties.in