Show graph for directory authorities voting on HSDir flag

I was reading "Analyzing inconsistencies in the Tor consensus" over the weekend and it occurred to me we could make use of including graphs showing additional flag voting behavior, not just for the Running flag.

This ticket is about showing graphs for the HSDir flag. I think for those additional flags it might be enough, though, to just show a graph for how many relays the directory authorities voted for getting that flag.