ENH: Bring back the QIIME colors - fixes #310

Discrete coloring using the QIIME-defined colors is now an option in the 
colormap selector under the colors tab.

getDiscreteColor now takes an optional "map" argument to know whether it is
using the ColorBrewer or the QIIME list of colors, defaults to ColorBrewer as
that is Emperor's default.

Finally there's a note in the ChangeLog describing this change.

Fixes #310.