Implement Null Graphics context

[Groogy]

Graphics context was designed so we could support several different versions and not only GLFW OpenGL. Should implement a null graphics version which can be used for testing purposes where you want a proxy interface that compiles but does not actually create a graphics context.

Requirements

• Should not open up Window context
• Should not open up OpenGL context
• Should not allocate textures or VBOs
• Interface should still work as if it was a real graphical context.