Restore support for BlendTexture property

Closes: #602

src/celengine/render.cpp

@@ -3257,9 +3257,7 @@ static void renderSphereUnlit(const RenderInfo& ri,
     prog->use();
 
     prog->textureOffset = 0.0f;
-    // TODO: introduce a new ShaderProperties light model, so those
-    // assignments are not required
-    prog->ambientColor = Color::White.toVector3();
+    prog->ambientColor = ri.color.toVector3();
     prog->opacity = 1.0f;
 #ifdef USE_HDR
     prog->nightLightScale = ri.nightLightScale;

src/celengine/renderglsl.cpp

@@ -285,8 +285,6 @@ void renderEllipsoid_GLSL(const RenderInfo& ri,
     if (shadprop.hasEclipseShadows() != 0)
         prog->setEclipseShadowParameters(ls, semiAxes, planetOrientation);
 
-    glColor(ri.color);
-
     unsigned int attributes = LODSphereMesh::Normals;
     if (ri.bumpTex != nullptr)
         attributes |= LODSphereMesh::Tangents;