- Shared lines (same line on several phones)
  + Active lines stored in db
- Separate SQL mutex per profile
- New event skinny::call_state
- Clean port_message
- More protocol understanding:
  + stimulus may have call_id
  + off_hook may have call_id
  + set_ringer may have call_id and line_instance
  + New DisplayPriNotifyMessage
- Use Cisco terms for Call state
  + Congestion -> LineInUse
  + CallRemoteMultiline -> InUseRemotely
- Add line_instance to Lines table (relative position contrary to
  absolute position)
- Less assertions as FS already does some