Fixed an important issue introduced by me in the previous revision.

Note: - Fixed an error introduced to .pov file by adding an object statement for ambient light (POV use it on global settings statement). Thanks Kagehi for report it. [Micheus]
- The path for Images used in textures (pigment/normal) now is relative to the place where the exported file is saved. [Micheus]
- Added the function to get relative path into wings_u.erl.