Added support for 13w42b's new shades and white

In 13w42b, more changes were made to map colors: the previously unused fourth shade of each base color is now a darker shade than any of the other three. In addition, the second white base color (used by white wool and stained clay, added in 13w42a) has become slightly different, leaving it no longer identical to the white used by snow.

Tested again, of course, and it works for all relevant functions (in fact, the fractal generators look much better thanks to the new shades). Of course, this time only values in the "colors" resource changed, so there's no reason it shouldn't work.