#251 Center Mouseover tool tips

[Worlds Best Minsky Modeler]

Have tool tips pop up within the screen area, to avoid the need to pan or open discription box. This feature would bring Minsky's tool tips up to par with its "kind of" competitors.

There would be some sort of character limit per line, and some way to adjust the tool tip so it remains on screen, for example if a variable is on the right side screen edge, the tool tip pop up would appear to the the left of the variable.