Updates for incorporation into Flambe

Changed orientationChange to orientationUpdate. Removed disposal of accelerometer, and made instance persistent. Removed properties that allowed direct access to motion and orientation instances.

Signed-off-by: Bradley Baysinger <bradley@seven2.com>
More accelerometer updates to fit into Flambe

Separated EventGroups so they are independent. Added private NotifyingSignal1, so Accelerometer can stop when it is not in use.

Signed-off-by: Bradley Baysinger <bradley@seven2.com>