Improve connection notification text.

Show the server name if only one server is connected.
Clarify mention vs. query in notifications.
Do notification text formatting in notification code.

Don't rely on strings formatted for adapter usage, which also avoids
accidentially modifying those strings.
Also make sure to use the message body of the originating event, as -
depending on timing - grabbing the message out of conversation could lead
to the wrong message being listed in the notification.
Merge pull request #100 from maniac103/notif-text-fix

Improve connection notification text.