Rework the Growl preferences for Notification Center:

* It is now called "Notifications"
* "Sticky" is now called "Show until dismissed"
* "Priority" is now "Growl priority" and is disabled when Growl is not running
* "Growl notification" is now "notification" everywhere

Also removed (very old?) code that Adium used to warn users about Growl updates or prompt them to install Growl, I'm pretty sure this isn't relevant anymore now GrowlWithInstaller is dead.

Fixes #16146, fixes #16117