Replaced people list with tree, so I get automatic updating (and nicely alternating row backgrounds) there too.
Refactored all that weird atom API stuff for tree cell properties into its own function
Replaced hard-coded sender email address with a getter that retrieves email address of default identity. In the future this may need to give back multiple identities.
Sending a reply now automatically marks conversation as not needing a reply; incoming message automatically marks it as needing reply.