Issue 33... keybinding discuss...

I think we need to add in something here to state exactly what a key binding
really is.
 
I think that we need to state that a key binding may be an entirely
iundependent entity or may be bound to other entities defined in an
underlying PKI and reflect the status of those entities - this is up to the
issuer to decide.
 
So if a key binding is reflecting the status of an X.509 cert and the cert
is revoked by any means then the key binding is automatically revoked.
 
I think this clarification will also help the policyidentifier definition.