Add behdad.Arc.distance_to_point() and use it
Fix numpy array usage
Improve arc-bezier error bound

Simplifies the code.  But there's a factor of two that I can't explain.
For now, put it in.
Put bask a .125 approximation scale (to get equivalent results as other algorithms). distance_tolerance_square seems to be different from flatness criterion
Corrected plot title/NTESTS