InDrawingMode Mouse Events

This adds event triggers for the InDrawingMode set of mouse event handlers.

I needed to add a mousemove event handler that fired without turning off
free draw, and imagined that others could use this functionality as
well.

Event strings are formatted using the typical non-namespaced DOM format, i.e. without
colons.
Merge pull request #1835 from noslouch/drawingmode-mouseevents

InDrawingMode Mouse Events