Ottava Clefs (try 2)

8va Treble clefs added. See Request #236 for background -- There are still about 7 too-many commits here, but the net result is 4 files changed in a manner that should be easier to see. 
Since they're all the same. I'd make it just:

Clef.sizes = {
  "default": 40,
  "small": 32
}

And remove the point size from `Clef.types`