fast_data: add option to archive files instead of delete.

[jtniehof]

This requires a little background. The fast_data.py script solves a particular operational problem we have with PSP, where we generate new versions at a far greater rate than we want to keep. This script is set up to delete files that are not the newest version but are newer than a certain date, so we can clean up after the period when data are downlinking and new versions being made on an hourly basis. It's not fully documented and long-term I need to generalize parts of it, get the documentation going, etc.

But in the short term, I needed to archive the files rather than delete. This involves marking as not on disk, and move into another directory not managed by dbprocessing, so the files are around but "dead to dbprocessing".

This also picked up a SpacePy dependency for this particular script.

PR Checklist

• [X] Pull request has descriptive title
• [X] Pull request gives overview of changes
• [X] (N/A) New code has inline comments where necessary
• [X] (N/A) Any new modules, functions or classes have docstrings consistent with dbprocessing style
• [X] (N/A) Major new functionality has appropriate Sphinx documentation
• [X] (N/A) Added an entry to release notes if fixing a major bug or providing a major new feature
• [X] (N/A) New features and bug fixes should have unit tests
• [X] (N/A) Relevant issues are linked in the description (use Closes # if this PR closes the issue, or some other reference, such as See # if it is related in some other way)

Since there are no docs for this now, I didn't have time to write up the entire script and just add in the docs of what changed.

[jtniehof]

Looks like the docker auth (#51) isn't working anymore. Will have to track this down later.

[jtniehof]

Got CircleCI running by making a new Docker user, but now there's an issue where SQLAlchemy has changed the name for postgres, https://stackoverflow.com/questions/62688256/sqlalchemy-exc-nosuchmoduleerror-cant-load-plugin-sqlalchemy-dialectspostgre . I'll have to see how early the new name is available and open another PR.

[jtniehof]

'postgresql' as the dialect name goes back to at least 0.6.