Make resizing large submodel windows easier

 [introduction cut] I find it is very difficult to click on the outline of the submodel accurately enough to be able to resize the window. I have tried snapping to grid which helps a little, but it is still a bit intermittent. It would be nice if this were made slightly easier in future releases (or is there an option box somewhere to type in the height and width of the box?)

Submitted by Jonathanm for wookie from http://www.simulistics.com/forum/graph-functions .