Implement a new action `delete` in etk filters.

[saggu]

If mydig sees a doc, which it got from ES, with action delete set, it should delete it from the ES if mydig sees a doc with action discard it should NOT load that document in ES, but it does not need to delete it from ES

[saggu]

@szeke still relevant ?

[szeke]

I forgot how the filters work, did we implement them?