Charger: Improve screen on/off scenarios

In charger-mode, power off/on screen as required, for efficient
charging.
Turn on screen on power-key press rather than on key-release.
On charge-cable removal, kick animation to show the correct battery
level.

Change-Id: I74eaf8681466c44dbd76a820adf154053e0fc43a
Signed-off-by: Pavan Kumar S <pavan.kumar.s@intel.com>
Signed-off-by: Jenny TC <jenny.tc@intel.com>
Signed-off-by: Yong Yao <yong.yao@intel.com>