plugin XEP-0346: "Form Discovery and Publishing" implementation: this implementation replaces the former non standard node schema, and works in a similar way (the schema is put in a separated node instead of a special field, thus it will now work with most/all PubSub services, and not only SàT PubSub). The implementation has been done in a way that nothing should be changed in frontends (bridge methods names and arguments stay the same). The nodes are modified, but if values are taken from backend, it's automatically adapted.