XWIKI-17054: Notifications macro and Activity (legacy) macro only showing wiki wide updates

- instead of adding a separate filter preference for the subwiki
  make sure the reference to pages and spaces are absolute
  by prefixing them with the "currentWiki"
- for this add the "currentWiki" back in the data-set
  generated by the notifications macro
- also added "toString()" methods to a few classes
  which helped in debugging the unit tests