new Mouse(canvas, world, callback)
Create and start mouse obj, args: a model, and a callback method.
The canvas upon which we track the mouse. If a string is given, get the HTML element by that name
callback(evt, mouse) called on every mouse action
Start/stop the mouseListeners. Note that NetLogo's model is to have mouse move events always on, rather than starting/stopping them on mouse down/up. We may want do make that optional, using the more standard down/up enabling move events.
this Return this instance for chaining