UserListView and UserItem were added as the backbone of the user-list,
and the (currently unused) Caya message CAYA_SEND_INVITE was established
for inviting users to rooms.
Some menus were reworked (e.g., pop-ups of the RosterListView) or
generally tweaked to be more sensical or consistent.
ALT-↑ and ALT-↓ change the active conversation, based on its position
in the main window's ConversationListView. If a conversation is
registered by the main window, and no other conversation is selected, it
is automatically selected.
Now all active conversations will be listed in the main window, in a
ConversationListView. Clicking one of the items will open its
conversation window as you'd expect, etc.