mod_muc_markers: replace configurable multi-marker tracking with better system Now tracks a single marker, but automatically applies rules from the XEP about "higher" markers implying "lower" markers - i.e. "displayed" implies "received". Still, just a single marker is tracked and synthesized at all times (the one configured with muc_marker_name).

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

module:log("error", "mod_smacks_noerror is deprecated! Just use mod_smacks and load mod_nooffline_noerror if you explicitly disabled offline storage (mod_offline)");