Add GDAS to Unidata TDS

[lesserwhirls]

Thanks to Carissa at NCEP / NCO, GDAS is now available on CONDUIT - w00t! The header looks something like:

data/nccf/com/gfs/prod/gdas.20180628/gdas.t12z.pgrb2.1p00.anl !grib2/ncep/SSIGFS/#000/201806281200F000/VWSH/2 K*m**2*kg-1*s-1 POTV! 000299

so will probably go with something like (testing on lead):

#
# ------------------------------------------
# - Global Data Assimilation System (GDAS) -
# ------------------------------------------
#
# GDAS 1.0 degree analysis only
#
CONDUIT	^data/nccf/com/gfs/prod/gdas\.(........)/gdas\.t(..)z\.pgrb2\.1p00\.anl
	FILE -metadata
	${DATA_DIR}/native/grid/NCEP/GFS/GDAS_1p0deg_ana/GDAS_1p0deg_ana_\1_\200.grib2

I'm checking to see if any forecast grids are being shipped, as well as if it's only the 1.0 degree GDAS, or if 0.5 degree and 0.25 degree are included.