Fix for non-polygon Edge.Cuts

[sej7278]

Most fabs want vscore lines on the Edge.Cuts layer, this means that the panel has various lines for rails and vscores that aren't strictly board outlines and this causes an error with the 3Dviewer as it cannot identify the board outline, it also fails the DRC.

Potentially we could move from lines to a series of (overlapping?) rectangles that would then be polygons. Not sure if that would help though.

Also could do with a way of detecting the line width of the Edge.Cuts layer, at the moment we're defaulting to 1.0mm same as KiCad.

[sej7278]

Also noticed that if you panelize a board with a nice rounded edge, it removes the rounding. Not sure if any fabs would be able to panelize a rounded edge anyway.