Conflict with multi-valued properties and @sort

[ehedgehog]

When there are multi-valued properties, the current result-set to JSON translator relies on rows being grouped by ?item and enforcing (or not, see issue #28) that ordering with a SORT or GROUP.

If the user specifies an @sort, that grouping is (except by coincidence) lost.

I believe the fix for this will require using the @sort to generate a sorted result set which is streamed to (possibly) disc, noting the multiple values (possibly also on disc), and then restreaming the sorted result set to the client, with the first occurence of each item having the saved multiple values injected and all subsequent rows with that item being dropped.

[ijdickinson]

I can't really tell from the discussion what the state of this issue is now. Opinions? Close, leave or work on during the next milestone? It hasn't held up any of the HMLR apps.