Authenticator preloading/caching/fragmenting

[andersk-auto]

krb5 authenticators are big -- so big that they might not fit in a notice header, let alone leave any room left for other things like class, instance, or recipient. So, instead of including them in the header of every notice fragment, we should figure out a way to delivery an authenticator to the server once, in a way that can be fragmented (i.e. as part of a notice body), and then reuse it for sending multiple notices.

[andersk-auto]

Imported from trac issue 95. Created by jhutz@CS.CMU.EDU on 2013-02-16T19:20:21, last modified: 2013-02-18T01:22:18