working with multiple textures, and some more readable examples for shaders

[tzukpolinsky]

Hello
For an academic project I'm creating in Haifa University, I tried to use the ModelViewer tool to load multiple textures.
In the first attempt, because in geometry_obj the texture names are given using an iterator and in the shader there is only one texture "texture_0", I couldn't use the program as is.

So I attached the texture names to the object names,and in GLDraw changed the structure of the function.

I hope you could integrate it in the repository, because loading and working with several textures is a painful subject across the web.

Thank you in advance
Tzuk Polinsky