component AP gateway: events: - XMPP Events <=> AP Events conversion - `Join`/`Leave` activities are converted to RSVP attachments and vice versa - fix caching/notification on item published on a virtual pubsub node - add Ad-Hoc command to convert XMPP Jid/Node to virtual AP Account - handle `Update` activity - on `convertAndPostItems`, `Update` activity is used instead of `Create` if a version of the item is already present in cache - `events` field is added to actor data (and to `endpoints`), it links the `outbox` of the actor mapping the same JID with the Events node (i.e. it links to the Events node of the entity) - fix subscription to nodes which are not the microblog one rel 372