If a user does a notice search that should return no matching notices, the RSS feed / API results for that search currently returns all notices instead of no notices. This fixes it so that an empty list is returned instead.
Add an array of arguments to isReadOnly() method of actions, to let
them change their results depending on what actions are called.
Primarily used by the 'api' action. Ideally in the future that will be
multiple actions. But this might still be useful.
