added Flag as value type
moved Batch to BatchBlock
renamed Choice to ChoiceBlock
made merging of parameters for ValueParams consistent (fillFrom and overwriteFrom are inverses of each other now)
made iteration over Multiple<T> type params easier
initial schema param blocks

Added a "name" property that lets a rule match a specific notification.
Added a "response" property that lets a rule specify a response when it matches.

Reviewed by Richard.

Added a mechanism for preventing classes of notifications from being displayed, controlled by the notification_visibility.xml file in the viewer skin.

Reviewed by Richard.