Added event triggering

CSS styles should be fixed, and javascript events 'denoto-keydown',
'denoto-keyup', 'denoto-writenote', and 'denoto-erasenote' now function.
Keydown/keyup are triggered on denoto-keyboard, and writenote/erasenote
are triggered on denoto-pianoroll.
Removed unused code

Removed code that made it appear that whitekey has event handlers that
blackkey does not.
Added transport bar

Added transport bar with events. Image attributions are in the comments
of the transport bar webcomponent
Fixed position bug

Fixed bug where mouse coordinates were relative to screen rather than
relative to the pianoroll canvas
Fixed mouse coordinates in pianoroll

Made a better fix that takes page scrolling into account
resolve merge conflict
Merge branch 'tw' into develop