Fix xmpp tests
xmpp: fix error handling
Return 'not-allowed' when save collection (update only)
xmpp: make occi_iq conform to XML schema
Collection update ok
update and save or authorized for both capabilities and collections. In these cases, save or treated like update
Fix xml parsing and xml tests
xmpp: user mixin creation ok
Use store and backend for actions
xmpp: action ok