Ottava objects for clefs (Treble 8va/Treble 8vb)

Added an ottava object to new treble_8va and treble_8vb clefs which are added as a second, zero-width glyph to denote music that sounds an octave higher than written (piccolo music) or an octave lower (some guitar transcriptions). Added tests to clef_tests.js. What doesn't work and I'll need some help with, is the clef change, since I am unclear about how to add two glyphs via a clefnote object. If anyone can help with that I'll work out the metrics for the other common 8vas (essentially just, bass_8vb; I don't know of any usage of another).

(also added .project to gitignore -- generated automatically by Eclipse; hope no one minds).

First Vex.Flow pull request, so please feel free to tell me what I should NOT be doing, so that I can do better in the future. Still new enough on Javascript that I want to get things right. (just learned about branches for pull requests...)
It's already a rather large stave.  I decided instead to divide the Clef tests into two tests -- one draws all the clefs at the beginning and a single .addEndClef at the end. The other draws one clef at the beginning and all the clefs as .addEndClef.  This seems closer to expected usage actually (rarely would someone want multiple clefs at the beginning or end, and I'd imagine never both, so this catches all possible and esp. likely usages)