added bench.py demo which prints tree build and render times
added Vertex to python binding, NormalVertex is now its subclass
Bugs
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* Mingw + SSE does not work
Future Plans
============
* UV texturing
* PlanarMap should allow to choose normal axis
* Container should implement Shape interface to allow building hierarchies
* Container should allow local space transformations
* generalization: Camera "shader" (ray generator), surface shader and maybe light & background shaders
* put everything into a namespace
* stochastic oversampling
* absorbtion of refracted rays in dense materials (can be computed using shape distance and some 'absorbance' constant)