mod_vcard_command: a simplistic way to get and set vcard data for registered users Use "prosodyctl get user@example.com" to print the XML to stdout, and "prosodyctl set user@example.com /file/name" to set the vcard info from an xml file.

This module writes out a traceback to `traceback.txt` in Prosodys data
directory (see `prosodyctl about`) when the signal `SIGUSR1` is
received. This is useful when debugging seemingly frozen instances in
case it is stuck in Lua code.