Second revision cleanup of ORTC API draft

Changes to RTCConnection:
- added attribute socket
- added attribute state
- added attribute role

- removed method getLocalSocket
- removed method setLocalCandidate
- renamed method setRemoteCandidate to addRemoteCandidate
- renamed method update to gather
- renamed method addStream to send
- renamed method receiveTrack to receive
- removed method addDtmfHandler
- renamed method getSendingStreams to sendingStreams
- renamed method getReceivingStream to receivingStreams
- renamed method tracks to sendingTracks
- removed method track
- added method receivingTracks

- removed event onconnected
- removed event ondisconnected
- added event onstatechanged
- removed event onaddstream
- removed event onddtmfhandler
- added event onnetworkchanged

Removed "autostart" boolean flag to send stream since now can construct "RTCTrack" object before calling send thus paramters can be tweaked before they become active.

Made DTMFStreamTrack object into a constructable derived class of RTCTrack

Added RTCDataChannel object

Added RTCStream object

By no means perfect but a lot clean up has happened to make the interfaces clearer!