A new feature in the visualiser - clipping

[sgenoud]

I finally found some time to finish this new visualiser functionality: clipping.

I often found myself wanting to be sure that a tolerance is well implemented (and seen myself using other tools to do that). Now I can just use the clipping functionality.

As always, feedback welcome!

[tve]

Something Id love to see in the visualizer is to be able to easily toggle a bunch of items on/off (view/hide), where items would be shapes, clipping places, and markers (lines or points that mark stuff but don't get exported). This way instead of fiddling with entering a Y position for the clipping plane in your example one could return a bunch of clipping planes from main, whose position got calculated.