Smart Radio: improved and simplified decision making logic
Smart Radio: take tethering via mobile network into account
when making decision about switching to power saving mode when screen is off
Smart Radio: option to delay power saving mode after screen turns off
Useful when user needs to turn screen on/off frequently to check for
something. Power saving mode will be activated after defined delay
expires. Since it's possible to set rather large delay (e.g. 30 minutes)
we use AlarmManager to schedule switch which will work even when device
sleeps.