Lit shader fixes

Fixes two issues: 
* vColor was being multiplied into the final output twice (once in the subroutine and once in the main() method).
* The code divided lightt intensity by ldist, an uncommon way of introducing inverse-distance illumination dropoff.  Since the light is in View coordinates, this made simple scene design very difficult.

You've changed this from a point light to a directional light.  Because the length of the light to point is no longer used,  the light can no longer fall-off with distance.