Add VideoStreamInfo to Request for Proxy->VM

Added 'videoInfo' optional field of type VideoStreamInfo to Request.
The proxy shall send a message with this field set to the VM's input
server immediately upon connecting so as to provide the input server
the necessary WebRTC setup information prior to the client sending its
'offer'.

Change-Id: Ic7ce56b0a20106ef80a5d5c1122c1a669277fa4a