Create HOA with button.

No phoning-home of the HOA yet, nor proper integration of HOA
session/app.
Merge branch 'master' into hoa

Conflicts:
	lib/unhangout-routes.js
Merge branch 'simplify-session-state' into hoa

Conflicts:
	public/js/event-views.js
	public/js/models.js
	public/js/video.js
Fix merge mistakes
Full HOA creation, persistence, and event-wiring
Fix play-for-all
Merge branch 'master' into hoa

Conflicts:
	test/test.youtube-embed.selenium.js
Fix tests from merge
Clean up HoA session lifecycle

Split server-side HoA model concerns into separate subclass,
ServerHoASession.

Implement auto-muting for lobby videos when user joins HoA.

Add "previous videos" control to admin page which lists
titles/thumbnails from youtube api.

Move "Join Hangout-on-Air" control to inside video controls area.

Switch Join hangout-on-air links to use session redirector.  Simplify
the `getSession` handler and update it to recognize HoA's as well.

Add HoA details to /admin/.
Move `event` out of default express locals
Add throttled broadcasts for performance.

Currently only used for session participant lists.
Decrease probability of event leaving in simulator
Add public chat logs of all chat history.

To keep the UI for this sane, refactor the way welcome messages are
displayed to make it a separate region rather than a
pseudo-chat-message.  This requires changing the slightly finnicky
scroller styles to scroll on the parent div.
Create chat-log dir on load if it doesn't exist
Replace event embed modal with in-page controls

Collapse all video embed controls into a single in-page view.
Merge branch 'comment-archives' into hoa
Add import for logger

This is baffling -- not sure how things ever worked without this, but
it's throwing an error now.  Require a logger in video-sync.
Re-send hangout-broadcast-id only when changed

Also, clean up some comments.
Switch button/link status when hoa has 0 connected
Add minimal event overflow handling

If there are more than conf.EVENT_USER_CAP users connected to an event,
redirect new users to an overflow page.