BGE Shaders: Adding color, dist to light include

Color is the lamp's color multiplied by its energy.
BGE Shaders: Allow disabling of custom shaders

Unchecking custom shaders in the UI was not reverting the viewport to the
default material. This is now fixed.
BGE Shaders: Removing libcode from custom shaders

Adding the libcode to the top of the shader code caused problems, such as
not being able to specify a version. Including the libcode will need to be
handled differently, such as through the include system.
BGE Shaders: Adding support for sampler uniforms