Graphical renderer quality improvements: First Stage

[arthurmco]

First part of the rendering improvements I want to add, just the sufficient for the future assets to look acceptable.

• Specular lights
• Shadows from the directional light
• Skybox (helps with the light & for future light reflection)
• Handle materials that emit light
• Anisotropic filtering (that terrain texture is awful)

With those things, we might be able to receive nicer assets, like meshes and textures, and they will look, at least, good.