Add direct handling of quadratic beziers to save compute time and number
of points. Update cubic interpolation to reduce number of points
generated for a given smoothness
Cache data on open and used cached data to avoid multiple re-calcs
Remove minimum line length and number of segments and replace with
standard max error level. Allows us to specify the tolerance of bezier
interpolation
(Copper shapes, on the other hand, can. Since we use
GetItemDescription() to report DRC errors and the like,
it's better to have it report the net even when it's
<no net>.)