Revert "Upgrade versionCode to 16 (0.11)"

This reverts commit 75889a76cabaa5de517b32c93dabae98d2c6b8af.
Add debug lines for flash screen semaphore
Fix flash screen semaphore issues

Fix problem where semaphore was released once per bell, but acquired
only once per set of bells, leading to excess permits.
refresh background colours when changing preference
Protect AlertManager from mFlashScreenListener being null

Should never happen but better to be safe
Notify data set changed if service disconnected
Apply preferences in restoreBinder() rather than onStart()
Change root background colour to black (was transparent)