KML should automatically determine NS

[crschmidt]

With three different KML namespaces floating about, the KML layer should have support for automatically determining the KML namespace version in use.

If we don't do this, I forsee a lot of problems as more users start using the KML layer.

[crschmidt]

Search all nodes for Placemarks. once we have placemarks, store the namespaceURI from the node if it exists, and use that to parse the rest of the document.

The default namespace for output is still 2.0. All tests continue to pass, and new tests have been added.

[sderle]

This patch seems fine, but what if a user wants to set the kmlns manually in code? I don't see it as a blocker if they can't for now, so please commit.

[crschmidt]

I can't imagine a way in which that would make sense. I'm going with this for 2.5RC4, and we can revisit later if it comes up again.

[crschmidt]

(In [4798]) Pullup for KML needs to automatically determine the namespace of the document it is handling. (Closes #1044)