Added docs for __replaceable__ property.

lib/python/Products/OFSP/help/ObjectManagerItem.py

@@ -114,6 +114,27 @@ class ObjectManagerItem:
       'REQUEST' -- The current web request.
       
         This object is acquired and should not be set.
+
+      '__replaceable__' -- Object ID policy flags
+
+        Objects placed in an ObjectManager can have a special property,
+        '__replaceable__'.  This property controls the policy surrounding the
+        ID assigned to the object.  Currently this property can only be
+        set in Python.  There are two flags which can be OR'ed
+        together:
+
+        ObjectManager.REPLACEABLE -- Normally, ObjectManager does not
+        allow new objects to be created using an ID that is already in use
+        in the container.  If the object has the property '__replaceable__ =
+        ObjectManager.REPLACEABLE', however, users are permitted to replace
+        the object with another object having the same ID.
+        
+        ObjectManager.UNIQUE -- Sometimes you need to be able to set up
+        a "component" object that won't be overridden purposely nor
+        accidentally in subfolders.  Setting '__replaceable__ =
+        ObjectManager.UNIQUE' will cause ObjectManager to disallow creation
+        of objects of the same ID in subfolders.  This has the effect of
+        enforcing a unique object ID policy.
     """
     
     def title_or_id(self):