Add $recursive filter option to allow filter to apply for all child frames

[kzar]

Background

We need a way to have a filter for a page apply to all it's child frames. This can allow us to prevent the circumvention of filters by nesting adverts within a frame of a different domain.

What to change

Add the new $recursive filter option to the core filter code. When used a filter should match pages contained within frames based on both the domain of the page and the domain of all parent frames recursively.

This will be especially useful for whitelisting filters but presumably others as well.

[sebastian]

Filters are generally recursive, e.g. @@||example.com whitelists all URLs with the domain "example.com" as well as any third-party resource loaded as part of a page or frame hosted on "example.com".

So I suppose that we are only talking about the new filters to disable generic filters here. I think those filters should be recursive by default (or mandatory), to match the behavior of exception rules.

[kzar]

The decision in IRC was that the $generichide and $genericblock options should always apply recursively as with the other whitelisting rules making this extra option redundant.