API for votes / vote_events

Probably don’t want these long term, but add them now for consistency,
and for seeing what’s going on
Fix motions data format

Standardise the IDs; don’t nest so much stuff into votes. Don’t add all
the @type-s
rename as voteit-api

instead of voteit-server
Rename load_* as reload_*

Versions that do upserts should be reload_*, so we can also add plain
bulk-load versions.
Add bulk loaders

bulk_load_{parties,people,motions}
Remove issues code from manager

issues now live elsewhere, so we can delete them from here
Delete the reload_* commands

Bulk loading is so much faster that it’s plausible to just delete and
bulk_load
no need to call them as bulkload* any more

As bulk loading is all we do, just call them load*
Rename reset() deletealldata()

for consistency with the other delete commands
aggregate examples should use party_id
Document bulk loading.

Update the README to show how to bulk load, with example documents.