Digests should be defined as "Default" rather than "Custom"

Similar to #1348768: Activity log rules should be defined as "Default" rather than "Custom", Digests defines its rules as "Custom" which makes it impossible to see when a site-admin has customized a status beyond the exported default.

Per http://drupal.org/node/298634, "Furthermore you need to modify the '#status' or 'status' properties of rules and rule sets. Set it to 'default' or 'fixed'. Fixed means, that the rule (set) is hidden from the UI and can't be customized by users"

The attach patch does this.