add libbatteryservice

IBatteryPropertiesListener is used by clients such as BatteryService to
receive notifications of changed battery/power status (from healthd).

IBatteryPropertiesRegistrar manages registrations of
IBatteryPropertiesListener clients.

Add BatteryService native header with defines from BatteryManager, and
class BatteryProperties to pass battery/power status around.

Change-Id: I44e2736e503b586794097b7b9d31d07fefd9b15a