This allows us to create Buddy objects as soon as we see a contact on the
server. For contacts not on trusted servers, or seen in anonymous MUCs, we
create a Buddy identified by JID instead (so we have some way to talk
about the anonymous contact within the Sugar API).
The concept of "trusted server" means a server which we trust to validate that
users with a keyID as the username part of their JID do in fact have that key.
Currently we just pretend that olpc.collabora.co.uk does this - in future, the
school servers will do this validation by using key rather than password
authentication.
Also create Buddy object paths based on the keyID or JID (for easier debugging).
