Disabled indexing of annotations.

2 reasons:
- annotations are not bound to a 'property' anymore, instead to a 'path'.
  The index updating mechanism would need to be adapted
- indexing of annotations is done by the Annotator now which is
  listening for all interesting document changes
Another (bugfix) iteration on Annotator.

Now is doing annotation indexing on its own, in a more advanced
way (-> hierarchical index).
Fix regression.