Embed xml3d

Embed the xml3d scene declarations in the main htmls in all the standalone examples, except the custom material using OpenCTM one. All others use now a little loadxml() util func in examples/xml3d

Removes quite many files, the used-to-be separate xml3d-htmls and the little js files that each example required to load it's own data. Makes examples/xml3d dir look cleaner and adding more example straightforward with just a single new file to get a scene.

Is important also because this is how xml3d is specified to work. What is missing still is automatic display of the scene when just the <xml3d> tag is added, without a script call. Should be easy/trivial with a body on-load handler or so, could check what xml3d.js does, but is left for next step anyhow as needs some care.