Runtime toggle of navbar

This adds the framework support for enabling the Navigation bar
on devices with hardware keys. It is toggled from Settings, and
depends on device-specific support for the KeyDisabler hardware
control

Change-Id: I88fecb2ca1e8613591c327a93f53909b00239cd8
Dispatch keys to a device specific key handler

Injects a device key handler into the input path to handle additional
keys (as found on some docks with a hardware keyboard).

Configurable via overlay settings config_deviceKeyHandlerLib and
config_deviceKeyHandlerClass.

Change-Id: I6678c89c7530fdb1d4d516ba4f1d2c9e30ce79a4

DeviceKeyHandle: The device should consume only known keys

When the device receive the key, only should consume it if the device
know about the key. Otherwise, the key must be handle by the active app.
Also make mDeviceKeyHandler private (is not useful outside this class)

Change-Id: I4b9ea57b802e8c8c88c8b93a63d510f5952b0700
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

DeviceKeyHandler : Allow handling keyevents while screen off

Some devices require the keyevents to be processed while the screen
is off, this patchset addresses that by moving the filter up in the call
hierarchy.

Change-Id: If71beecc81aa5e453dcd08aba72b7bea5c210590
Merge changes If71beecc,I88fecb2c into kk4.4

* changes:
  Dispatch keys to a device specific key handler
  Runtime toggle of navbar