Fixed Multi-Camera and Multi-Shader issues.
Put another way: Implemented multi-camera, multi-shader ability.
Decoupled Camera shader (i.e, desired shader to render Camera's physical object)
  from the concept of the "Active" shader.
Added "Rendering Camera" and "Current Shader" state to the Engine.
Merge branch 'master' of https://github.com/UMLComputerGraphics/GraphicsProject