Attempt to fix an issue where capabilities are no longer included in NOTIFY starting from the second NOTIFY using the presence information for a given user. I also reworked the code because it was not really fair and efficient to put capabilities in all tuples, since there is no correlation between tuples (linked to PUBLISH) and capabilities which are advertised in REGISTER. Instead the capabilities are listed in the said "default element", which is the element that contains information provided by things other than PUBLISHes, such as AuthDb and RegistrarDb.