Active Display: Add always show pocket mode. [1/2]

Currently pocket mode is either on or off and when no
notifications are available it doesn't turn on.  This
adds an option to allow active display to come on even
when no notifications are available, showing the time
and allowing the user to unlock the device.

PS2:
Add unlock icon to center of the ring.

Conflicts:
	packages/SystemUI/src/com/android/systemui/statusbar/policy/activedisplay/ActiveDisplayView.java

Change-Id: I14043256e0202b497c0e9f3c64aa796c1b2becac