[dom] Move out of color-base module

Currently, the `dom-style` module depends on `color-base` module only for
falling back to calculate computed style on legacy Opera (<= 12), but the
latest Opera (15+) is almost the same Chrome (`Y.UA.webkit` returns truth
actually). Many core modules are depending the `dom-style` module, I expect
that many YUI modules and applications will benefit to faster from more
than a little by this change. I also hope that this resolves #1621.