[Bug?] Constants.ANIMATION_DURATION should be exposed as a setting and not be a constant

[iguanajuice]

The only way to change the animation duration for on-screen and grouped notifications is by editing the source code; this is awful.

Ideally, the existing "transition-time" setting should be used instead of this constant, or perhaps "notifications" under "widget-config" should have "animation*" settings like "menubar" does