Added a bunch of functionality

There is a note painter which paints wherever the mouse is until turned
off.

There are also "fretpainters" at the bottom which will paint all the
notes in a fret.

You can show the note names or the note intervals relative to the
selected root.

There is a root pull-down and a set Root mode with the next mouse click.

There is also a notegroups browser which will replace any painted notes
with scales or arpeggios (and update the root). I haven't figured out
the best way to present chords yet.

The paint by Interval color mode will continue to paint with this note
group.

You can drag the notegroups to the notegroup dashboard. From there you
can single click to convert painted notes to the new notegroup. These
notegroup "buttons" can be resorted and double-clicked to trash.

There are also Player controls which will cycle through the notes
relative to the speed spinner.

The generate link works pretty much the same.