* Make the render window accessible from within GL2PSUtilities during
  export.
* Move Draw3DPath from GL2PSExporter to GL2PSUtilities.
* Minor changes to private API function arguments.
* Generalize code for projecting points from world coordinates to GL2PS
  device space.

Change-Id: I358b5e0bfeb7bedee5565a0855dcbba913ecc558