Bug 1071009 - [Loop] Expose bitrate, frames dropped and frame delay to a...

...pplications via TB library.
Added all information given by tokbox including framerate on encoder/decoder side, frames dropped and bitrate. RTP information also available.
Tokbox doesn't provide framedelay information. That info must be retrieved from gecko.
Don't use c&p, this is the same that at the else condition, please see comment:
https://github.com/mozilla-b2g/firefoxos-loop-client/pull/340/files#r21078223