[view] add a new entity_call method to entity view protocol, allowing some to work with not yet created entities. Also, start considering 'eid' form parameters where we only consider 'rql', so we can move on bloquing arbitrary rql inputs (more to do on this...)

[idownloadable] refactor IDownloadable primary view to make overriding easier

[web] ajax_replace_url superseed build_ajax_replace_url, more generic and relying on the json controller (closes #750090)