Botskeleton

Multi-output bugfixes
* BREAKING CHANGES
* upload_media had to go to make multi-output work in a reasonable way. I did this without
thinking, which is why 2.2.0 wasn't marked as breaking. I realized I didn't have an easy way
to restore it, so I'm just admitting this is breaking now. Replace calls to upload_media
followed by send_with_many_media just with send_with_many_media - it will do the upload_media
appropriate for the given service.

* BUGFIXES
* send_with_many_media in outputs has unnecessary (and broken?) use of splat operator
* mastodon actually extremely misused splats
* didn't pass up extra keys while adapting old birdsite records to new multirecords
* mastodon output didn't pass media ids when sending correctly, meaning images never made it to
toots

Multi-output
* FEATURES
* Support more than one site!!!
* Rework output from skeleton so it doesn't assume only one site output.
* Move birdsite to a new output separate from the main one.
* Add support for Mastodon.
* Change record formatting to multi-output site, convert old records in-place.

NOTE:
Entries beyond this point are backfilled.
They should be relatively accurate, but won't be exact.

Error handling
* DEV/BUGFIXES
* add framework for handling errors
* call error handler for errors
* will call out to dm_sos if it can't handle the error
* add default handler for birdsite's duplicate tweet error, which bots hit a lot

Bugfixes
* DEV/BUGFIXES
* pass over errors a few more times to make them store correctly and not crash the program
* JSON-dump their dict when creating the TweetRecord
* also do some type-checking when trying to assume things about error structure

BOTTILITIES
* DEV/BUGFIX
* we expect errors to be objects, so just pass the whole object in TweetRecords

BOTTILITIES
* DEV/BUGFIX
* errors can't be indexed, just stringify them when storing in TweetRecords