Fixes #2000

Fixed Blender importer to work with Blender 2.60, add option for importing workers or non-worker models.

Fixed more examples to use worker-less format. All examples should work now.

Only Max exporter should be left to change.

Problem was having too many concurrent workers opened at once. Garbage collection apparently works very slowly on workers. Solution was to close them manually, after model data is sent to main thread.

Also some progress with Blender scene exporter. Some scenes now export correctly, though monkey test scene got worse, even with less hacky code.

Single quote property names and hex numbers are not valid in JSON.

Also some fixes along the way to properly handle vertex colors in loaders.

Many things still broken, but we move forward.

Only Blender 2.56 exporter and OBJ converter were tested. If somebody is using other ones, please reexport some files to be sure they work.

Also fixed quads vertex color bug in WebGLRenderer and did small optimization of face state handling.