[Tizen] Sensor support

SensorProvider class is designed to abstract sensor framework and
provide all sensor related notification for xwalk (currently support
rotation, orientation, will support motion, compass, geolocation
and gyroscope in future). TizenPlatformSensor is the platform
depended part for Tizen mobile system. It is designed to not depend
Tizen in build time.
Merge pull request #769 from zliang7/master

[Tizen] Sensor support for crosswalk