RTP Timeout handling

Terminate RTCSession when iceConnectionState turns to 'disconnected'
Fix #127. Make in dialog requests atomic. Thanks @gavllew
Hold/Mute implementation
Remove duplicated code
Delete duplicated code
Enhance accuracy when setting the direction of mediaStreams
Enhance Session Modifying internals

RFC3261 Section 14
Merge branch 'hold' of github.com:versatica/JsSIP into hold

Conflicts:
	src/RTCSession.js