- convert a combination of JID and optional pubsub node to AP actor handle (see
`getJIDAndNode` for details) and vice versa
- the gateway now provides a Pubsub service
- retrieve pubsub node and convert it to AP collection, AP pagination is converted to RSM
- do the opposite: convert AP collection to pubsub and handle RSM request. Due to
ActivityStream collection pagination limitations, some RSM request produce inefficient
requests, but caching should be used most of the time in the future and avoid the
problem.
- set specific name to HTTP Server
- new `local_only` setting (`True` by default) to indicate if the gateway can request or
not XMPP Pubsub nodes from other servers
- disco info now specifies important features such as Pubsub RSM, and nodes metadata
ticket 363
