Cosmetic changes
FIx contact match in 200 response to REGISTER

- Adapt to new JsSIP.URI style
Cosmetic change. Delete extra log lines
- Multi browser support (first approach).
- JsSIP.Utils.isWebRtcSupported() moved to JsSIP.WebRTC.isSupported().
Hack window.RTCSessionDescription into JsSIP.WebRTC.RTCSessionDescription (compatibility).
Merge branch 'multi-browser' of github.com:versatica/JsSIP into multi-browser