dvb:probability should be 1000 by default
Created by: mattjuggins
If dvb:probability is absent in the Metric's Reporting descriptor it should default to 1000 (a reporting player) as per DVB spec (Clause 10.12.3.3). The typo that referenced dvb:priority instead of dvb:priority has been corrected in the DVB spec now for some time and it's probably fair (and safe) to remove the fallback to this.
Made some changes to be more explicit about attribute names and default values. I based these on how the DVB extensions are handled for BaseURL elements.
Straight off the bat, I work for the BBC and you should be able to see I'm part of the BBC's organisation on Github. We signed the CLA in 2014 (point 4): https://github.com/Dash-Industry-Forum/dash.js/wiki/Meeting-Minutes#minutes-april-4th-2014