[Merge Request] Notify

[Jorge Villaseñor]

I have done some work to unify the notify API to behave consistent and
less annoying. The first movement was to group the Pounces in a dialog
like the mail notifier which add each pounce to the same window.

In the im.pidgin.cpw.masca.notify I have added this same behavior to
the _error, _info, _warning parts of the API. This way we will have
only 3 notification windows that will pop-up only at the *first*
event, this way we can prevent getting a lot of windows with a
recurrent error, notification, etc like the old issue with msn
contacts or when trying to get into a xmpp MUC with an already used
name.

I want to propose to merge that branch to i.p.p to be in the next release.

-- 
Masca