Fixes jitsi-meet-prosody install dirs and jitsi-meet rules.

A more proper way to install dirs for jitsi-meet. A fix for install of jitsi-meet-prosody which needs only its own /usr/share/doc folder. A cleaner way to use the rules file and a fix in the quick install howto (right now the packages work without fixes on the latest Ubuntu release only, not on a generic Debian based install)