A couple of improvements to the bulk collada importer:
(1) handle hierarchical nodes in the visual scene
(2) handle the <triangle> element of geometries. This was done the lazy way: convert <triangles> to <polylist> and call the function that was already there for handling <polylist>
Merge branch 'master' of https://github.com/diva/libopenmetaverse
Removed an unnecessary import.