The angle needs to be added to the start angle.
Add tests to cover this:
* Check end point is correct
* Check midpoints are within tolerance
This would have prevented the bug fixed in 5813164d1,
as well as the bug fixed in this commit.
As well as failed tests, this manifests when routing across
Edge.Cuts arcs (unless they happen to start at 0 degrees
staritng angle).
Expose as expected failure to prove tests catch it.
Fix to follow in separate commit.
183f4fe9a5