Sort perf graphs' series in gen graphs

This will have a pretty substantial impact on graph loading times, and will
allow me to rip out a bunch of the javascript functionality.

Sorting used to happen online with the expectation that we might have more
complicated sorting in the future. e.g. sort based on the average of the last
weeks data instead of just sort based on the most recent day.

This moves sorting to gengraphs and stops sorting online. The functionality to
sort online is still in perfgraph.js but I'll remove it later assuming
everything goes well.

The actual sorting in gengraphs is a little kludgy because it takes the csv
that is generated, parses that and then sorts it before printing printing out
the now sorted csv.