NGDC endpoint source syncing with NcML updates

[brianmckenna]

@rsignell-usgs

With the new UI coming together, there's been a big effort to reference the CF compliant standard_name field instead of the NetCDF variable name (which has varied greatly between models).

This will lead to a new round of NcML(adness), the good news being modifications should be easier to find. I've gone through two small changes just to test the type of updates needed, and that they should be doable via NcML. (TL;DR - they are)

Two examples, I just made small changes for testing to:

• eta (standard_name changed to _sea_surface_height_abovegeoid) http://comt.sura.org/thredds/dodsC/comt_1_archive_full/inundation_tropical/MDL_SLOSH/Hurricane_Ike_final_run_egm3/00_dir.ncml.html Kelly should have some other comments about SLOSH
• salt (standard_name added _sea_waltersalinity) http://comt.sura.org/thredds/dodsC/comt_1_archive_full/shelf_hypoxia/DAL_ROMS/2004-2009_climatology_obc_with_oxygen_inst_rem_20layers/00_dir.ncml.html

These are live at those endpoints, but the NGDC indexed endpoints don't seem to reflect the underlying NcML files in the /data/comt_1_archive directory.

What do we need to do to bring those two together?

[brianmckenna]

pinging @kknee since I'm neck deep in code and her task list is better than mine.