[feature] Depthmap cannot process circles or arcs

[kerstinsailer]

If a drawing contains circles or arcs (as for instance in a curved organically shaped building), Depthmap cannot process them and either converts them into zigzag lines, or completely ignores them.
Sometimes it helps converting circles or arcs to polylines in a CAD programme, but sometimes it doesn't (don't know why).
It would be great if this could be fixed.

[SpaceGroupUCL]

The algorithms is made to work like that. So let's say it's a new feature.

Maybe this can be split into 2 requests as I think it might be easier to cheat a bit in the dxf conversion code.