[Sensor] Updating start method documentation

[Sensor] Updating start method documentation

+ Adding list of possible error types launched in ErrorCallback.
+ Adding some brief info to the method description.
- Removing UnknownError error type from the list of synchronously thrown
exceptions because only TypeMismatchError may be thrown synchronously.
The change of implementation was requested by GunWang Jeong (ethan.jeong).

Change-Id: I1998214f1b0d5538409f3952fc5a22accd008060
Signed-off-by: Szymon Jastrzebski <s.jastrzebsk@partner.samsung.com>