[Yt-dev] Needs review: data labels

[Matthew Turk]

Hi guys,

I need someone (Jeff?  This is sort of in your wheelhouse) to look at
this patch:

http://paste.enzotools.org/show/99/

It's designed to change the way display labels are calculated for
plots, specifically slice and projection plots.  I'd like to commit it
and close #130, as it adds a display_name option to fields which
overrides the field name.

After review, I'll commit.

-Matt