Set light transform matrix irrespective of light type

WIP: Update light geometry based on camera

Change-Id: I689a9709e4d7618c3a72fb6ff1f6cb7385c04540
ENH: Added test for vtkRenderingExternal

TestGLUTRenderWindow demonstrates the use of the
vtkRenderingExternal module by rendering VTK objects in a GLUT
window.

Change-Id: I8bbbdc4a05b335b105da971217d0f5a31891b5a9
Replace baseline with MD5 sum

Change-Id: Idc0a3e50476cd1561e16bd782ba8f712f01c2769
Fix lighting for the external rendering module

Change-Id: Ibf7eb3aacc30a06b5e86e0dfd6cc8968e51f9556
ENH: Fetch viewport size for the existing OpenGL context

Change-Id: Iea3c3018085925e656db0199b4009bd6feb34e84
Cleaned debugging code

Change-Id: I005ad11461c166fef2747ba80677514ae6d8f334
Updated baseline for TestGLUTRenderWindow

Change-Id: I4a8dc633db6a4b170957deda1dfbed4a1de73081
FIX: vtkRenderingExternal module is OFF by default

Change-Id: I2cec13305e521d958362d15eaae75e0f8e73bbee