Notify me when a user returns from “away” status / joins one of the active channels

[zarino]

Would be a really useful feature when you need to talk to someone but they're either not connected, or marked as away.

We already poll for the userlist of each active channel – it just needs to store a list of nicks we're interested in, and raise a notification when they join / come back from being “away”.

[zarino]

This should probably be activated through a right-click menu option of "Notify me when back" on the userButtonView for that user, if the user is marked as away.

Would be awesome if the menu item was ticked once you click it, so you can see a notification has been "requested" if you later right-click their name again and they've still not returned from being away.