- C4::Letters:EnqueueLetter() is aware of new fields in message_queue table
- C4::Circulation::SendCirculationAlert() actually works
- C4::Category cleanup
- C4::ItemType cleanup
- C4::Message is a new module.
  It presents yet another way to interact with the message_queue.
  You can now take messages that have already been queued and modify
  their contents before they're sent out.

Signed-off-by: Daniel Sweeney <daniel.sweeney@liblime.com>
Signed-off-by: Galen Charlton <galen.charlton@liblime.com>