[1/2] Base: Toggle lock screen camera widget

Adds an option to enable/disable camera widget on lockscreen.

Settings: https://gerrit.omnirom.org/#/c/4702/

Change-Id: Ia2ccdd306956cddd8285c30ccceb759dff406366

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardHostView.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/NavigationBarView.java