Router per-message annotations version negotiation

Directly connected routers (and edge routers) exchange per-message router annotations.  In order to support the ability to modify these annotations in future releases, have a router advertise the format (version) of its message annotations.

This can be done via a new connection properties value which is set to the version of annotations accepted by the router.  Directly-connected routers would exchange these versions and agree to use the minimum version advertised.