Add non-intrusive notification system
* Service messages (e.g. authorization requests) are queued so user won't be bothered with unimportant messages.
* User can view the service messages in Kopete main window.
* A green flag in status bar or optionally KNotification will inform the user about new service messages.

New classes:
AddedInfoEvent - event which should be created when a contact added you into the contact list or requested authorization.
InfoEventManager - contains all info event objects
InfoEvent - base class for all info events
InfoEventWidget - widget for Kopete main window