plugin XEP-0384: OMEMO for MUC implementation: - encryption is now allowed for group chats - when an encryption is requested for a MUC, real jids or all occupants are used to encrypt the message - a cache for plain text message sent to MUC is used, because for security reason we can't encrypt message for our own device with OMEMO (that would prevent ratchet and break the prefect forward secrecy). Thus, message sent in MUC are cached for 5 min, and the decrypted version is used when found. We don't send immediately the plain text message to frontends and history because we want to keep the same MUC behaviour as for plain text, and receiving a message means that it was received and sent back by MUC service - <origin-id> is used to identify messages sent by our device - a feedback_jid is now use to use correct entity for feedback message in case of problem: with a room we have to send feedback message to the room and not the the emitter - encryptMessage now only accepts list in the renamed "entity_bare_jids" argument

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ping: get response time of an XMPP entity
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``ping`` is more or less the equivalent of the command of the same name on most OSes, but
for XMPP. It send a `XEP-0199`_ PING and wait for the answer. When (and if) received, the
time to receive the answer is shown, else the time to receive the error message is shown.
This can be helpful to quickly test the connection with the server or a device.

If you need to get only the response time (without text around), you may use ``-d,
--delay-only``.

.. _XEP-0199: https://xmpp.org/extensions/xep-0199.html

example
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Get reponse time of a server::

  $ jp ping example.org