#639 Deal with ENUM data

[Jeremy Faden]

ENUM is part of the rich header definition already - make some renders for it.

Like a barplot with different colors for each ENUM
like an overplot of a line color coded by ENUM

[Jeremy Faden]

Another URI that new users might try:
vap+dds:http://cdaweb.gsfc.nasa.gov/cgi-bin/opendap/nph-dods/istp_public/data/genesis/3dl2_gim/2003/genesis_3dl2_gim_20030501_v01.cdf.dds?ProVelRTN_label