Fix showing bump/normal-maps if object was not completly uv-mapped.
Implement show_normal_maps menu toggle

Only the menu entry was implemented, not the actual code.
Cleanup shader handling and fix normal shaders on older gl versions

Do not test texture available in shader, instead set it as a material
property, this should work on mac's and older OpenGL implementations.
Fix build error (warning)
Fix old OpenGL lighting

Only shaders worked, old lighting was messed up in the prev commits
Merge branch 'dgud/normalmap-bug'
Merge branch 'dgud/build_error'