oceancolor file naming

[raymondben]

Oceancolor files have changed their naming convention. I think it's a rolling implementation of the new convention, so not all products necessarily yet follow the new convention (but I have not checked). So we might need to support both old and new conventions. https://oceancolor.gsfc.nasa.gov/docs/filenaming-convention/

Implications include:

• https://github.com/AustralianAntarcticDivision/raadtools/blob/main/R/ocfiles.R#L37 filenames no longer use single-character platform abbreviation, "A" is now "AQUA_MODIS", "V" is now "SNPP_VIIRS", etc
• https://github.com/AustralianAntarcticDivision/raadtools/blob/main/R/ocfiles.R#L52 filenames encode dates as YYYYMMDD not day of year
• components of file name are now (mostly?) separated by "." not "_"