LockScreen: Fix crash when unlocking twice

This will keep track if the BroadCastReceiver is registered and
will unregister it only if so.

Change-Id: I040d710cf0927394f36b2e3da251ac5a988ce1d6
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>

Conflicts:
	policy/src/com/android/internal/policy/impl/keyguard/KeyguardSelectorView.java
Framework: Remove Needless Preference

PS2: Missed Line
PS3: Further Settings Clarification:
        If Reverse/State_one double
        click action: launch action
        long/short (they can still
        choose "skip" if they don't
        want to launch anything).
Change-Id: Ie220b7eb2c16d0ce81c444eea5936c681ea55a9a

Conflicts:
	core/java/android/provider/Settings.java