Validate android extension object values (API level, etc) against APK library.

[Lanchon]

In the 'patched-application' plugin, add a task that warns or fails if the values set on the android extension object (API level, etc) are incompatible with the values from the APK library being patched. Otherwise, make the 'apk-library' task annotate the APK library manifest with the minimum requirements. Both options require parsing the 'yml' file produced by apktool.