Configuration for lock and UI sound levels

Define two integers in the platform configuration to
 define the sound level for lock/unlock sounds, and
 UI sound effects.
Use the corresponding value in KeyguardViewMediator for the lock sounds.
Use the corresponding value in AudioService when playing sound effects.

Bug 6448481

Change-Id: Ie238f5eb1645e395412864d93447ac4049f7e54b