SeaBASS ".sb" filename extension update

[OB SeaBASS - cwproctor]

The filename extension ".sb" is now officially used to identify the SeaBASS data file format. As of today, the entire SeaBASS archive has been updated and existing files have been renamed to use this suffix. Prior to this, data submitters were free to pick their own extension, and SeaBASS files could be found with a variety of extensions such as ".dat", ".csv", ".txt", etc., which have now been stripped off and replaced. The standardization of the .sb suffix will make SeaBASS files easier to recognize, organize, and work with, and it fits with the format being formally recognized as an approved NASA Earth Science Data format as of several years ago. The renaming was also required for an upcoming project that will make some changes to the online systems used for ordering and downloading SeaBASS files.Data submitters should take note of this ".sb" suffix requirement. Please use the new suffix for all future data file submissions (SeaBASS data files only; it isn't used for documentation and other metadata files), otherwise SeaBASS data managers will rename your files. Also, when generating new SeaBASS file names, please keep in mind our general naming recommendations so your file names are informative and unique.Data users should be minimally affected, but should note that a large percentage of historical files had their names changed slightly as of April 10, 2020. Thus, due to the updated suffix, a file downloaded today will likely have a different name than the same file downloaded before this. Other than the metadata header "/data_file_name" being updated to reflect the changed file names, the contents and format of the data files are unchanged.~Chris