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.
Now all instances of sending messages (bar status changes) to a
conversation's CayaRenderView only happen when attached to the window.
Messages sent by user appear after the protocol confirms it's been sent
(IM_MESSAGE_SENT), rather than appearing right after the user sends it
to the protocol (IM_SEND_MESSAGE).
Logs are now re-enabled (since they can safely be appended under any
circumstance).
Removes explicit setting of sizes in ConversationView and StatusView,
allowing them to be resized appropriately. Also rearranges StatusView
somewhat, so that it's more friendly to smaller sizes. (The avatar is
moved from being beside the status menu field to being beside the
nickname textbox.)
All chats now stay in a single window, which removes and switches its
current ConversationView with the appropriate one using
Conversation::GetView().
This is a stepping-stone to merging the ChatWindow into the MainWindow.