Some new features

Hi,

So, this is my first pull request, you could read what I made, and what I would like to made after.

Done :
- press ctrl + alt to change the editor mode
- add a demoMod ( to have something similar to glsl.heroku / shadertoy )
- add some BRDF (Ashikin, OrenNayar, fresnel)
- remove the auto-rotate, and  add a buton to reinitialise rotation

Suggestions for the future : 
- Display FPS
- Uniform management 
- more snippets ( Cook-orrance, Solver, Noise, Distance-Field, Mathematiques tools ...)
- autocompletion with CTRL+Space for Snippets

Thanks a lot for your tool Thib, I am happy to contribute !

Have a nice evening

*§*