fix a bug in webrtc stream signaling stack to improve stability

Fix probem with 720p video full screen display on chrome browser

Update RocketChat/Rocket.Chat#12 Prefix settings and oembed_cache collections with rocketchat_

Add web-rtc in-band signaling stack as an optional (not installed by default) package

rocketchat_embed_cache. Handle error where oembed_cache doesn't exist.

Fix RocketChat/Rocket.Chat#12 Standardize collection names

restore webrtc code removed by recent merge commit

Update Collection variables to use new rocketchat_XXX collections and
migrate data (v9.coffee) from old collection to new collections.  After
migration, drop old collection (data.ChatXXX) via rawCollection access.
Note: rawCollection access added with Meteor version 1.0.4.

Messages stream. Flow Router implementation. Render off-screen of rooms.

# Conflicts:
#	client/routes/router.coffee
#	client/views/app/room.coffee

Conflicts:
	client/lib/chatMessages.coffee
	client/lib/collections.coffee

# Conflicts:
#	client/views/app/room.coffee