Revert "Add ColorDef.link, unlink and toCSS, see https://github.com/phetsims/bamboo/issues/16"
Revert "Add ColorDef.link, unlink and toCSS, see https://github.com/phetsims/bamboo/issues/16"

This reverts commit 88a48039

phetsims/scenery,phetsims/scenery,phetsims/scenery