Constructor which creates a window with given width, height and title (title of the actual physical window, not of the plot). Calling gfx.Window() creates a window with a default size of 400 by 400.

For example: 

	w=gfx.Window(100,100,'title')

To call any of the methods of Window one can then do for example: 

	w:cls();
	w:plot({0,1},{0,1},'rx-');

Equivalently, one can also write: 

	gfx.cls(w);
	gfx.plot(w,{0,1},{0,1},'rx-');