Blender Internal: Add "Lamp Data" shader node that allows shaders to acquire information such as light vector from specified Lamp.

For now this provides the following outputs:

- Color
- Light Vector
- Distance
- Shadow
- Visibility Factor

Note: Color output is multiplied by the lamp energy.  Multiplication of
color*max(dot(light_vector,normal_vector),0)*shadow*visibility_factor
produces the exact same result as the Lambert shader.

Many thanks to Brecht for code review and discussion!

release/scripts/startup/nodeitems_builtins.py

@@ -111,6 +111,7 @@ shader_node_categories = [
     ShaderOldNodeCategory("SH_INPUT", "Input", items=[
         NodeItem("ShaderNodeMaterial"),
         NodeItem("ShaderNodeCameraData"),
+        NodeItem("ShaderNodeLampData"),
         NodeItem("ShaderNodeValue"),
         NodeItem("ShaderNodeRGB"),
         NodeItem("ShaderNodeTexture"),