Switch to Browser gamut mapping method

[facelessuser]

Browsers have still not settled on what they are doing for gamut mapping. Currently we clip by default because no other browser has implemented the recommended CSS gamut mapping method. We've implemented it, but do not use it by default. Once we update ColorAide, we will have a faster GMA method available as well.

There is currently a debate between browsers and spec writers as to what the GMA will end up being. I want to track this here so we can resolve as soon as there is agreement and the dust settles.