started coding basics of new processing code
Documentation for the MediaProcessor
More steps towards a working reprocessing system.

Fleshing out the base classes and setting up some docstrings.  Not
everything is totally clear yet, but I think it's on a good track, and
getting clearer.

This commit sponsored by Ben Finney, on behalf of Free Software Melbourne.
Thank you all!
More progress towards the new reprocessing infrastructure: args updating

This commit sponsored by Elizabeth Webber.  Thanks, sis!
"initial" reprocessing subcommand now works!

We are on our way now to a working reprocessing system under this
redesign!

This commit sponsored by Bjarni Rúnar Einarsson.  Thank you!
`gmg reprocess available --action-help` now tells you processor arguments!

Every reprocessing action possible can inform you of its command line
argument stuff!  Is that awesome or what?
Whitespacin' it up.
Moving celery setup to the right place

This commit sponsored by Jose Manuel Zueco Lazaro.  Thank you!
Steps toward working "run" reprocessing command.

This commit sponsored by Philippe Casteleyn.  Thank you!
Should be enough to get to the point where you can actually initialize a processing command now.

However, it doesn't celery task-ify it...

This commit sponsored by Catalin Cosovanu.  Thank you!
Updating to the point where we can allllmost run with the new reprocessing code

This commit sponsored by Odin Hørthe Omdal.  Thank you!
That manager.process() line no longer made sense
Renaming the processing manager stuff to be less ambiguous.

BONUS COMMIT to Ben Finney and the Free Software Melbourne crew. :)

IRONY: Initially I committed this as "media manager".
Marking the initial steps for processing
Record the original state of the media entry in the processor

This allows our processor to make some informed decisions based on the
state by still having access to the original state.

This commit sponsored by William Rico.  Thank you!
Factored the get_orig_filename from processing state and put it to use.

This commit sponsored by Vincent Demeester.  Thank you!
Theoretically the last steps to get reprocessing working for initial & images

Haven't tested it yet though :)

This commit sponsored by Samuel Bächler.  Thank you!
Fixing the MediaProcessor context manager so it actually, you know, works :)

This commit sponsored by Mikiya Okuno.  Thank you!
A couple of fixes to stupid things I did while coding this.  And it WORKS!

This commit sponsored by José María Serralde Ruiz.  Thank you!
Fixing normal submission of media (well for images anyway)