[2/2] Add lockscreen rotation as an optional rotation setting

Taken fom:

http://review.cyanogenmod.org/#/c/55016/

PS8
respect system config as default value

Change-Id: Icfd4344ffaf6987fe51b2a28df47593d9b3b3c0c

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