sort conversation by time of entry creation, not just id
improve presentation users in the dialogues list

For dialogues between users where neither is the current user,
the user without mod/dialogue:manage permission is presented
as the primary in the dialogues list. Also, when viewing a dialogue
between two users neither of whom is the current user, the 'Dialogue
between X and Y' form of message is presented.
typo in 'dialoguebetween' lang/en string
Fixed settings file, had weird new lan_string() calls
Merge pull request #26 from jonof/usq-improvements

Improvements to dialogues list presentation