Loading analytic BRDFs as glsl shaders

Motivation

Disney's BRDF explorer loads shaders as glsl files. (Actually, these are in ".brdf" format and appear to be slightly different from what I see in vertex and fragment shaders?) In my opinion, we want to do the same thing because:

1. We want to be compatible with industry-standard formats.
2. Disney's tool already contains many pre-implemented BRDFs. We want to use these instead of "reinventing the wheel" for each one.
3. We want our system to be extensible - a developer shouldn't have to understand our codebase to write a new analytical shader. They should just write one program in a standardized language.
4. We don't want to have to write two seperate shaders - one for the render preview window AND one for the lobe visualization.