[pyassimp] Fixed transformations in bounding box computation
[pyassimp] Rework material dict

- Normalize the names
- Do not create numpy arrays for the properties
[pyassimp] Remove obsolete code
[pyassimp] Added a new pygame/sdl based OpenGL viewer

This viwer uses a shader-based pipeline and has working keyboard/mouse
controls.

Makes a starting point for 'modern' OpenGL apps.
[pyassimp] Simplified and beautify simple_opengl_viewer.py

Since the new SDL based viewer is much better suited to interactive exploration, simplify
the basic OpenGL viewer to make it an easy introductive read.
[pyassimp] Minor formatting in README.md
Merge pull request #10 from severin-lemaignan/for-upstream

[pyassimp] New sample application based on SDL/pygame + various fixes