Database clean up

[dseliahu]

General ticket for any db clean up that needs to happen. We can just keep this ticket open and add to the list until enough things stack up that we need to address it.

• Remove duplicate volunteers (Saloni Desai is one, there may be others)
• backfill first and last name by splitting name field
• add volunteer id to requests
• add completed request ids to volunteer
• manually populate language and car of volunteers we've already interacted with