Make oceansites_index.txt file URL public

[ngalbraith]

Chrome and Firefox have both discontinued support for ftp, so the published URL, ftp://data.ndbc.noaa.gov/data/oceansites is effectively defunct. (Note: On a Mac, browsers do offer to open the link in the Mac 'Finder' app, but trying to do that as a guest fails – with the error ‘The share does not exist on the server’.)

A URL that does work, without NDBC log in credentials, is https://www.ndbc.noaa.gov/data/oceansites/oceansites_index.txt.

Action items:

• fix this URL in the DFRM, and any other documents where it appears.
• add this, or a link to a more ... appealing list of files/datasets to OceanSITES.org and/or to a public area on the GDACs, unless it is already there

[hmsnaith]

Would the threads server address be more useful? https://dods.ndbc.noaa.gov/thredds/catalog/data/oceansites/catalog.html

[ngalbraith]

To the human eye, the catalog displays only a list of site names. Although the index file is a blunt instrument, it has metadata that can be used to find out what we have, when and where it was collected, and when it was updated. That info is more helpful than a list of site names. Unless we provided a link to a script that could process the catalog, I think we're better off posting a link to the index file (both would be good).