mod_pubsub_serverinfo: implemented all basic features This commit replaces the earlier proof-of-concept to a solution that: - reports on remotely-connected domains - uses disco/info to detect if those domains opt-in - publishes domain names for remote domains that do so - caches the disco/info response

-- this module is deprecated, log an error and load the superseding module instead
module:depends"smacks"

module:log("error", "mod_smacks_offline is deprecated! Just use mod_smacks!");