Bug fixes and improvements...
- Remove old defines from DeepEnd.h (DES_FRIEND_INVALID and DES_FRIEND_SELF)
  - You should use the runtime constants DESFriendInvalid and DESFriendSelf, respectively.
- Add ability to reference chat contexts by UUID.
  - New method: -[DESFriendManager chatContextWithUUID:]
  - New property on DESChatContext protocol: uuid
- Add action sending (/me) to DESChatContext.
  - New method: -[<DESChatContext> sendAction:]
- Update DHT info API for new Core.