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. 
they're all the same for this font, so I've made the change, but I think that it's possible that other fonts might have different sizes per clef, so it may need to be reverted later.