Preserves Relative and Smooth values as initially set in the path. These can be overridden by setting `relative=True`, `relative=False`, `smooth=True`, `smooth=False`.
Rebuilt the core SVG path parser. This was required to pass W3C Path17 and Path20 tests. The code now correctly parses svg arc flags as either 0 or 1 rather than a float. And will stop parsing paths if unknown characters are found within the data.