Space Constraints for Document Autocomplete

When selecting a document with Autocomplete in a Documents Field of Display Property Macros the search is limited to the delegate space.

We should search on all available spaces, not just those on the delegate spaces.

Authors and Template Authors may put constraints on their autocomplete spaces by the Autocomplete Constraints parameter.

Therefore we add a new property 'Autocomplete Space Closure' that allows to define the basic search closure, defaulting to the delegate space.