Add Shader Program to front of list in WebGLRenderer

[TravisThomp]

WebGLRenderer only allows for adding programs that run after the splat rendering program has drawn to the canvas which means that anything a sequential programs draws will lay on-top of the rendered splats, this is annoying for programs that render items like a grid to the canvas.

This can be fixed by added a function to add a shader program to the front of the list inside WebGLRenderer

Also, this class should store the programs list outside the constructor so people can have direct access to the program list if they extend the class.

[TravisThomp]

nvm, this actually isnt needed :p