Add double tap sleep feature to secure lockscreen

 - pin and password: double tap the entry view
 - pattern: double tap anywhere on the pattern view
 - slide lock: double tap lockring to sleep

Change-Id: Ib04605f6c1bcffb19d3616a7d3e8564da4ef11ed

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardSelectorView.java