distance flag for changing object ordering

[bgoglin]

v2.0 distance matrices are currently ordered by physical index. We could add some flag to force ordering by logical index. And maybe add some output attributes to say that these indexes go from 0 to N-1 or so, so that lookups are easier.

Sorting would at least be useful because lstopo --distances reports logical indexes by default, hence often out-of-order unless NUMA physical indexes are in the same order (often fails when we have NVIDIA GPU NUMA nodes).