PROTON-293: Use more conservative initial message size estimates

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1467972 13f79535-47bb-0310-9956-ffa450edef68
PROTON-260: initial checkin of addressing_and_routing.md


git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1468073 13f79535-47bb-0310-9956-ffa450edef68