[fixed] Context menu out of screen

[mbartelsm]

In the old interface was the context menu would always be fully on-screen. If you right-clicked at the bottom of the workspace, it would pop up with an offset to compensate. This is no longer the case.

It is particularly troublesome as workflow in W3D keeps your focused object at the center of the screen, so if the menu is too long at that point, you have to bend over backwards to try to reach those last few items at the end.