[Geojson] Finishing the edits

[Martin Daly]

>> 2. You need to be able to distinguish between, for example, a
two-point 3D LineString (with xyz) and a three-point 2D
>> LineString (with xy), both of which have six ordinates.
>
> How about a "cardinality" field, holding the dimension? (i.e., 2 or 3)

This whole topic (encoding coordinates as an array of array of doubles
versus an array of doubles) came up before.  Sean answered it here:
http://zcologia.com/news/573/rethinking-json-for-geospatial

"Should you represent geometries as lists of lists in your analysis or
visualization software? Probably not, for the reasons that Matt
mentions: memory overhead and speed of access. But we're just talking
about the wire format here, and representational clarity trumps
computational efficiency on the Web. Limitations or quirks of our
implementations shouldn't be engraved into our standards."

M