Setting up the basic game objects

The majority of the work that went into creating Alien Attack was done in the object classes, while almost everything else was already being handled by manager classes in the framework. Here are the most important changes:

GameObject revamped

The GameObject base class has a lot more to it than it previously did.

class GameObject
{
public:
  // base class needs virtual destructor
  virtual ~GameObject() {}
  // load from file 
  virtual void load(std::unique_ptr<LoaderParams> const &pParams)=0;
  // draw the object
  virtual void draw()=0;
  // do update stuff
  virtual void update()=0;
  // remove anything that needs to be deleted
  virtual void clean()=0;
  // object has collided, handle accordingly
  virtual void collision() = 0;
  // get the type of the object
  virtual std::string type() = 0;
  // getters for common variables
  Vector2D& getPosition() { return m_position; }
  int getWidth() { return m_width; }
  int getHeight() { return m_height...