Introduce Material.Set so you can change all attributes within a material or shader
This allows you to create materials completely in C#
Add Color
Update comments
Merge pull request #606 from Facepunch/proceedural-materials
```cs
public static void SetupCustomMaterial(ModelEntity myModel)
{
Material m = Material.Create( "my_cool_material", "simple" );
m.Set( "g_vColorTint", Color.Red );
m.Set( "g_flMetalness", 1.0f );
m.Set( "Color", Texture.White );
m.Set( "Roughness", Texture.White );
m.Set( "Normal", Texture.Transparent );
myModel.SetMaterialOverride( m );
}
```
https://files.facepunch.com/ognik/1b0511b1/199966083-b7e9a595-98b3-4e9d-8cc0-b5850db444f8.png
