Added original "toon/cel" shader back. To make old maps work again

Shader: "Cel (Legacy)"

The reason why it was left out at first:
- I wanted to make a toon shader that supports MULTIPLE lights, but its going to take a bit of work. For now only ONE directional light will work, just like before. Also, things like xray and vertex snapping wont work with it. This sorta ruins the consistency of the shader list. Just remember "Legacy" = slightly broke...