WLFilters: set default values
- Respect different default values for 'limit' and 'day' in RC and WL.
- Make 'latestrevision' respect 'watchlistextended'
Introducing 2 properties to ChangesListBooleanFilter
- activeValue: The value that defines when a filter is active. Most filters are active when they are set to 'true' but 'extended' has no effect when it is 'true' and applies filtering when it is set to false.
- isVisible: Whether this filter is visible anywhere. 'extended' is not visible in the legacy form but it is activated from preference or URL. When understanding form submission, it should not be assume to be 'false' when not present in the request.