Refactor color-interpolation so we can use color spaces

We want to do more color interpolation than just the SVG standard values, so we want to refactor the enums currently used into being the Color Space system directly.

We add a interpolation attribute value matching and interpolation check into the color space API itself and a manager function to parse it out.

We then move SPStyle to use the new parser instead of being an enum.

Interation into the rendering code will come later, so we keep the old enum for just those parts until the time it can be replaced.