Closing Telehash links

[zlatinov]

The links are closed only locally (link.close()), but other parties need to know the link has been closed as well. We're using HTTP transport for Telehash and it doesn't automatically close the connections, if a client goes offline.

lib/comm.main.js, CommMain constructor (line 33)
lib/comm.main.js, CommMain.leaveGame (line 354)