This is only temporary, since we suspect that the calculation for the
receive direction is incorrect.

If there was no notification from the JVB about the connectivity status
it means it's connected. That's because the bridge does not send any
notification unless there is a problem.

Cleans up code. Paces the increase of connection quality. Take ramp-up
into account. Uses sending bitrate by default whenever possible (with
and without simulcast, as long as we know the sending bitrate and
resolution).

Updates the packet loss based calculation (used whenever we don't know
the sending bitrate and input resolution) with hard-coded thresholds,
so that it doesn't scale linearly (15% packet loss doesn't yield 85%
connection quality).

If Strophe drops the connection while not being asked to, it means that
most likely some serious error has occurred. One currently known case is
when a BOSH request fails for more than 4 times then the connection is
dropped without supplying a reason through the Strophe API
(the connection status simply goes to DISCONNECTED).