Removed unused AT PVector.
Added ComputeUV() to compute the unit UV vectors ov the viewing plane.
Removed U,V calculations from DrawPlane.
Added ComputeWindowProjction() To compute the projection of the display window
      onto the UV viewing plane.
Added DisplayWindowProjection() to draw the projection of the display window
      onto the UV viewing plane.
Updated DrawPlane to draw a grid in the UV viewing plane that properly fills
  the display window without needlessly overdrawing past the display window
  dimensions.
Corrected camera displacement when a key other than 'v' was pressed.
Assorted changes to improve separability of code and allow for future updates.