Detect Python version when running build.py script and let user know the script won't run in Python < 2.7, suggest a download link, then quit

Renamed Vector3 projectPoint() to applyProjection() as per @WestLangley suggestion in bb873d16.

Changed back some .projectPoint() to .applyMatrix4() as per bb873d16.

Renamed ShaderLib's 'normal2' shader to 'normalmap' as suggested in 4276c9f5.

@WestLangley I've changed most of the vector.applyMatrix4() to vector.projectPoint().
Feel free to change back the ones that aren't needed (or let me know which ones can need to be changed back and I will do it).

ShaderUtils relied on ShaderChunks so this created troubles when trying to use three-canvas and three-extras. Besides, better to keep a single library of shaders.

This is the bug I started the day with. And I kept finding other issues on the way. I think it's now fixed, but this made me realise how convoluted this exporter is :(