LockScreen: allow long-press actions from hardware keys (1/2)

Allow following actions with button long-presses on lockscreen:
- toggle flashlight (if available)
- play/pause/next/previous track selection
- toggle silent mode

Allow customizing of back, menu, and home buttons. Search
button events are completely ignored on the lockscreen.

Auto-detect hardware keys, only show appropriate menu
options based on the actual hardware keys available on the
device (or completely hide if there are no hardware keys).

Based largely on Danny Baumann's work from gingerbread.

Ported from CM10
Change-Id: Iff32736d00ca5d4122f64a6a861bbb0a1de9cca9

Fix home/menu unlock with long press hardware key
- Forward port of commit 2a572ee7
Change-Id: Ic2eb85542f8052fe1662244fe5e72ba12a98608b

Keyguard: Fix for home wake/unlock
sometimes device is waking and unlocking during the same keypress.
Change-Id: I72ea7611d39aac0cd03dfd5aa7036aeef7600140

Use sticky broadcast to convey torch state (1/2).
It doesn't really make sense to store the (non-persistent) state of the
torch in a (persistent) setting. As the torch is sending a broadcast
anyway, make that broadcast sticky and use it to convey the state.

Also unify the torch constants (actions, extras, activity names) at a
common place.
Change-Id: If845bef27cc79990794aa748dce18cfea3bac1f5

Fix Home/Menu/Back keys' unlock
Change-Id: Ibd3842b6ad8e037a2a9f8eb581e7c55900017b0f

LockScreen: allow hardware key longpress to put device to sleep
Change-Id: I54260e21c462bcabd9b6383e22f44d644630b4d3