|SOURCE|
[Common::BaseGameEntityRenderable2D]
* Added member function LoadContent, which loads graphical assets for the game
  entity, this must be implemented in derived classes
* From the test texture, Render positions the texture in the centre of the
  screen
[Common::GameEntityManager]
* SetRenderer member function stores the pointer to a SDL_Renderer in the class
* When AddEntity is called, the entity is checked if it is a renderable entity,
  if it is, then the class is cast to an appropriate type and the member
  functions related to initialising rendering are called
[Common::Player]
* LoadContent will load a test texture
[Common::Game]
* The game entity manager's SDL_Renderer is set after it is allocated