Remove unused code from vertexLighting_DBS_world_fp.glsl
Move object to tangent space transforms to the vertex shader for vertexLighting_DBS_world

This removes a few matrix * vector computations from the fragment shader and also frees up some varying slots.
Use the correct texture coordinates for glow maps and specular maps in vertexLighting_DBS_world

We couldn't use the correct ones before because we were hitting the 8 varying vec4 limit
Update error message to use constant instead of hardcoded value