Make the lock screen camera widget configurable (1/2)

Change-Id: Ia349c39937a56ee53c2c8ec2441d71ad081572e3
(cherry picked from commit c7133ae62a5a57cf4da3c6674c1a3140ef6e7534)

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java
Fix visibility of camera widget on insecure lock screens with DPM

The camera widget should be visible on an insecure lockscreen even
with the KEYGUARD_DISABLE_SECURE_CAMERA policy flag set.

Change-Id: I37ff905c6325be9120b16984d3401f334ad00e4c
(cherry picked from commit 5db9cec47d3de9a7399827c8a48038d1624cc827)