Adds support for color grading and adds some other rendering related tweaks.

* Adds support for color grading via a color grading lut (just out that lut in the graphics application of your choice together with a screenshot of the application and start tweaking away - don't forget to store the lookup table afterwards)
* Adds support for loading cubic 3d textures (currently loaded from a 2D texture atlas)
* Adds two sample color grading LUTs and makes the first one the default one for the scene
* Renames some of the textures in the texture folder two conform with our naming conventions
* Reduces the opacity of the outline but increases the density of outlines generated for blocks - makes the scene look nice and crisp without being overly annoying
* Tweaks explosion particle effect
* Removes some unnecessary OGL calls and adds some other minor cleanups