Added InputType struct to the Input class and its corresponding accessor and variable.
Added a default initializer to the KeyboardInput class to initialize the type as KEYBOARD
Updated the SceneCommand structure to have a magnitude and type.
Updated accessor for getting an input instance from the InputManager class.

We can now specify and input type to acquire and if the InputerManager has an instance of that type, it is returned.
Updated the KeyboardInput class to be named GlutKeyboardInput

This is very specific to glut, so thought it better this way.