- add example for python rna property update

- edit the copyright for blender specific cmake find modules

doc/python_api/examples/bpy.props.4.py

@@ -0,0 +1,20 @@
+"""
+Update Example
+++++++++++++++
+
+It can be useful to perform an action when a property is changed and can be
+used to update other properties or synchronize with external data.
+
+All properties define update functions except for CollectionProperty.
+"""
+
+import bpy
+
+def update_func(self, context):
+    print("my test function", self)
+
+bpy.types.Scene.testprop = bpy.props.FloatProperty(update=update_func)
+
+bpy.context.scene.testprop = 11.0
+
+# >>> my test function <bpy_struct, Scene("Scene")>