mod_rest: Map the XEP-0313 <fin> element to make paging work

mod_rest: Imply type=set for archive queries This is what makes GET /archive/{to} do the query instead of retrieve the form only.

mod_rest: Let 'type' be implied in path based queries This will make e.g. MAM queries work via GET /archive/{to}

mod_rest: Stop search when an implied type is determined Optimization only, as the iteration order is undefined. And not much since there's not that many entries in the implied_types map.

mod_rest: Add some convenience mapping to make MAM queries easier

mod_rest: Add support for mapping of XEP-0313 query iqs

mod_rest: Add XEP-0059 mapping Will be useful for MAM

mod_rest: Add XEP-0004 mapping for future reuse For use with MAM and such

mod_bookmarks2: Fix comparison The nick and password elements are children of the conference element, rather than the pubsub item element passed to the function.

mod_bookmarks2: Fix handling of nick and password elements This form of child retrieval fails when the stanza elements internally don't have an 'xmlns' attribute, which can happen sometimes for some reason, including when they have been constructed via the stanza builder API. When that is the case then the explicit namespace arguemnt does not match the nil value of the internal attribute. Calling `:get_child()` without the namespace argument does the right thing here, with both nil and the parent namespace as valid values for the internal attribute.