Send the tune only if ther is a change from the previous state
Add a receive_user_tune option (fix #2261)
Fix #1841 (User nickname)

- add a use_pep_nick boolean option
- use it as a nickname for roster contacts, but it does not
    supercede the user-defined handle
- send a <nick/> at the beginning of a normal chat
- not implemented in MUC (wontfix)
Fix #1839 (User mood/activity)

- Added as always new theming variables:
    CHAR_ROSTER_MOOD, CHAR_ROSTER_ACTIVITY (a SNOWMAN!)
    COLOR_ROSTER_MOOD, COLOR_ROSTER_ACTIVITY
- Added two new notification types in Theme.INFO_COLORS (mood/activity)
- Added new configuration options:
    display_mood/activity/tune_notifications (those can be set for a
    specific JID)
    enable_user_tune/nick/activity/mood
- Added /activity and /mood commands, with completions
- Moved the old /activity to /last_activity
- Details are show in the ContactInfoWin if there is room, or with "i"
  on a contact in the roster.