Update the XMPP Error in order to implement the RFC3920 chapter 9.3 (http://www.xmpp.org/specs/rfc3920.html#stanzas-error).
The XMPP Error will have a code, condition and type:
The code remainds the same as today.
There will be some conditions by default (like item-not-found) and users may create errors using them or new ones.
Available types will be: wait, cancel, modify auth and continue.
The new way to create errors will be using a condition and not a code.