Revert "Update Android support library v4 to r18"

- this reverts commit 401b350222c2b41ce58e46431aed5728d61f81fc.
- compat library r18 is incompatible with ABS

Signed-off-by: Owen Hart <owen@subsplash.com>
Update project target from android-14 to android-15

Signed-off-by: Owen Hart <owen@subsplash.com>