Skybox

[jtmzheng]

• Basic Skybox and cube map texturing support
• Moved some functionality out from Renderer and into the client
• Cleaned up ShaderController a bit
• Added a new shader program for Skyboxes
• Added bounding boxes to each model (useful for the next task)
• Optimized picking by using the bounding boxes instead
• Stuff left to do: -> Refactoring ShaderProgram and allowing for the client to set the ShaderProgram associated with a given model (different branch) -> Refactoring Model, Camera, and Renderer -> Fixing player movement -> Environment reflection and refraction (feature to add later on to Skybox)

[jtmzheng]

Also made Texture an abstract class after I realized there was more than one type.