mod_rest: Add special handling to catch MAM results from remote hosts Makes MAM queries to remote hosts works. As the comment says, MAM results from users' local archives or local MUCs are returned via origin.send() which is provided in the event and thus already worked. Results from remote hosts go via normal stanza routing and events, which need this extra handling to catch. This pattern of iq-set, message+, iq-result is generally limited to MAM. Closest similar thing might be MUC join, but to really handle that you would need the webhook callback mechanism.

  * Make groups optional
  * Make groups work with both posixGroup and groupOfNames