Fix remaining errors in frethandfinger.js + some minor refactoring
Fix remaining errors in frethandfinger.js + some minor refactoring

Silverwolf90/vexflow,aaronmars/vexflow,Huji/vexflow,aaronmars/vexflow,Tails/vexflow,Silverwolf90/vexflow,Tails/vexflow,Silverwolf90/vexflow,Tails/vexflow,Huji/vexflow,aaronmars/vexflow,Huji/vexflow