Skybox Support

[aryanbaburajan]

Is your feature request related to a problem? Please describe. As of now the engine does not support a Skybox, and thus the background is plain black which is not very pleasing to look at.

Describe the solution you'd like A Skybox support: A field std::string cubeMap[4] in the Configuration namespace, which users can choose the skybox to be set at initialization. And a method void SetCubeMap(std::string cubeMap[4]); in the Renderer class, to let users change the skybox after initialization as well.