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: I89af10f6262f674efe6cd5ae994bbcf85fab0861
Merge "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)." into jb-mr2