TODO

+ Contacts manager http://sipsimpleclient.com/ticket/123

+ Inbound Presence http://sipsimpleclient.com/ticket/130

+ Outbound Presence http://sipsimpleclient.com/ticket/118

+ Save configuration thread-safe

+ Make middleware unicode friendly http://sipsimpleclient.com/ticket/121

- Allow the FileSelector to compute the hash later, with a specific method
  which will be execute in another thread and which will notify the caller
  using notifications about the progress and when it's done, allowing the
  caller to continue

- End a session while in accepting state (requires session serialization
  http://sipsimpleclient.com/ticket/107

- Model file transfer after desktop sharing (use handlers on termination)
  have internal/external handlers (notifications based or file bridges)

- Use an ordered dict for keeping accounts in the AccountManager ?!?
  see http://code.activestate.com/recipes/576693/