Implemented a basic framework for node-based shaders.

Shader nodes will be used to define materials for stroke rendering, so as to
allow users to interactively configure textures.

release/scripts/startup/bl_ui/space_node.py

@@ -67,6 +67,16 @@ class NODE_HT_header(Header):
                 if snode_id:
                     row.prop(snode_id, "use_nodes")
 
+            if scene.render.use_shading_nodes and snode.shader_type == 'LINESTYLE':
+                rl = context.scene.render.layers.active
+                lineset = rl.freestyle_settings.linesets.active
+                if lineset is not None:
+                    row = layout.row()
+                    row.enabled = not snode.pin
+                    row.template_ID(lineset, "linestyle", new="scene.freestyle_linestyle_new")
+                    if snode_id:
+                        row.prop(snode_id, "use_nodes")
+
         elif snode.tree_type == 'TextureNodeTree':
             layout.prop(snode, "texture_type", text="", expand=True)