WIP: various fixes

- inheritance issue (can't depend on Class.prototype.super for deeply nested classes)
- date filtering and interpretation (for whatever reason, InboxApp times are in seconds since the epoch,
  while JS dates are milliseconds since the epoch).
WIP: example application for sending messages
WIP: list-threads example will now fetch threads with lastMessageAfter=2 weeks ago

Additionally, the example will sort threads by the date of the newest message --- so, it's easier
to view the results of the draft-messages example.