chat window layout enhancements

- use table/table-row for the main vertical fluid layout
- remote video now occupies full available width
- WiP
working layout for textchat/texthat/video for small/medium win sizes
sync with master
added chat layout development file
added offer/establishment switches to chat layout devel html
call now hides depending on call state; updated tests
sync with master
sync with master
sync with master
Merge branch 'full-width-video-in-chat-window' of https://github.com/n1k0/talkilla into full-width-video-in-chat-window

Conflicts:
	static/css/chat.css
Minor cleanups: log errors from gUM, comment about required pref setting, clearer use of Array.prototype.forEach