Renumbered errors

Renumbered all error messages.
Added ErrorManager import
Merge pull request #51 from LingoLasse/renumber

ErrorManager: Renumbered Locomote errors
Error Management

Error Management for Audio.
Changed error 807 to RTSP error code (401)
Changed event names

Changed event names to audioTransmitStarted and audioTransmitStopped
Fixed wrong event name
Added audioTransmitStopped event to error 813
Removed git comment