update stats in a single request at the end of payday
transfer balance during take_over()
add a branch.sql to deal with existing cases
add test to prevent regression
add a `context` column to the `transfers` table
refactor
factor query for elsewhere logins into its own method
remove XXX comment

Sessions are attached to participants, not elsewhere accounts.
don't show take-over transfers in charts
what matters is the number of accounts the participant can log in with
don't leave elsewhere accounts connected to archived participants
show transfers differently depending on context