This means you can have a pose bone for eg and get the path...
   pose.bones["Bone"]
 uses rna internal functions, so will work for sequence strips etc.
- StructRNA.get(), used for getting ID props without exceptions...
 val = C.object["someKey"]
 or..
 val = C.object.get("someKey", "defaultValue") # wont raise an error
- change rna property for testing if rna props are editable, test the flag rather then calling the function since the function depends on blenders state.
- fix a python exception with the ID-Property popup UI (when editing in more then 1 step)