The API Tokens tab gets a "Last used" column, so an unused token can be
told from one a script still needs. The token's last use is written when
it authenticates, at most once a minute (accounts.auth.TokenAuthentication,
knox's class with that one addition; the API schema describes it as
knox's).
A user has at most ten tokens; a new one is refused until one is
deleted. Expired tokens do not count, and are deleted when a new token is
made.
