- move more active properties into their collections:

scene.active_keying_set --> scene.keying_sets.active
  ...same for active_uv_texture. active_vertex_color, active_keyconfig, 

- move mesh.add_uv_layer() and mesh.add_vertex_color() into their collections
  also have them return the newly created layer and dont set the layer active.

  uvtex = mesh.uv_layers.new(name)
  vcol = mesh.vertex_colors.new(name)

release/scripts/ui/properties_data_mesh.py

@@ -272,7 +272,7 @@ class DATA_PT_uv_texture(MeshButtonsPanel, bpy.types.Panel):
         col.operator("mesh.uv_texture_add", icon='ZOOMIN', text="")
         col.operator("mesh.uv_texture_remove", icon='ZOOMOUT', text="")
 
-        lay = me.active_uv_texture
+        lay = me.uv_textures.active
         if lay:
             layout.prop(lay, "name")
 
@@ -341,7 +341,7 @@ class DATA_PT_vertex_colors(MeshButtonsPanel, bpy.types.Panel):
         col.operator("mesh.vertex_color_add", icon='ZOOMIN', text="")
         col.operator("mesh.vertex_color_remove", icon='ZOOMOUT', text="")
 
-        lay = me.active_vertex_color
+        lay = me.vertex_colors.active
         if lay:
             layout.prop(lay, "name")