Allow RosterItem to store and retrieve Presence stanzas
This extends the RosterItem to store a Presence stanza for the
case of new subscription requests.
This is serialized and stored in the database as usual.
There are getters and setters for the stored stanza, but also a
utility getter which can create a dummy stanza as needed.
Allow XML elements to be serialized
I've done this by imbuing ExternalizableUtil with the ability to
serialize and parse XML. This then allows lower-level strategies
to be entirely unaware of the nature of the string.
Higher-level code can then serialize XML, and trivially manage
serializing Stanzas.
Dave Cridland <dave@forwardhealth.co>
ef94fd74f385a6bd8c3d484a4a15485573219884
Actually remember the presence stanza need setting!
