[dpub] CSS Priorities Spreadsheet

During the call today, Ivan expressed interest in having some more detail
on the CSS priorities. I've just started such an attempt:

https://docs.google.com/spreadsheets/d/15IsDMPwSXx197Iqe4I9xh7K8anmJ5c0-OFEG7w0LHYM/edit?usp=sharing

I have lots of work to do here, but just wanted to know if this looks like
a useful approach.

Thanks,

Dave