Clean up mapper consents data

[cl8n]

• [ ] updater should be allowed null and set to that if the last updater is unknown. like the submissions sheet problem, need to see if google exposes data about each cell's last editor
• [x] mappers need to be loaded into users database
• [x] and beatmapsets

[huuishuu]

also:

• [ ] Clean up migrated data (delete/replace unrelated accounts)

  Mostly a result of mappers changing names and new users taking the old names and the data on the Google sheet not being updated to account for it.