Fix baseUrl port checks
Fix merge
Add participant tracking to gadget, facilitator

Gadget now posts a cross-document message to facilitator every 5 seconds
with the currently connected participant data, to be eventually used to
update ``session.connectedParticipants`` to include users who join the
hangout without the app.
Track participants who join hangout but not app
Restrict session messages to sockets in the room
Activities in unhangout facilitator
Select newly added activities by default
Implement 'hide app' button in facilitator
Fix facilitator about text
Fix participant JSON parsing
Improve styling for activity tabs
Fix race condition setting hangout-url
Add tests for setHangoutUrl; fallback gapi.hangout.data for sessionId
Fix editing permalink settings; add session creation tests