erp5_web_jabber_client: work for for avoiding messages loss

Add Semaphore functionality on adding Log to history.

Implementation of Delivery Receipt sending. Delivery Receipt hadnling is
not implemented yet.
http://xmpp.org/extensions/xep-0184.html

clients which support xep-0184
adnroid: https://conversations.im/ https://www.xabber.com/
linux: http://psi-plus.com/

/reviewed-on !76