Fix handling of extended names and sync traits in DataFrameEditor (possibly TabularEditor)

Using the DataFrameEditor's sync traits (`selected`, `dclicked`, etc) will not work when used in conjunction with extended name syntax for the object being edited.

```python
class MyModel(HasTraits):

data = Instance(pd.DataFrame)

def __init__(self, **traits):
HasTraits.__init__(self, **traits)
self.data = pd.DataFrame(data={'col1': [1, 2], 'col2': [3, 4]})

class MyView(HasTraits):

model = Instance(MyModel)
dclicked_record = Event

view = View(Item('object.model.data',
editor=DataFrameEditor(dclicked='dclicked_record')))

def _dclicked_record_fired(self, new):
print('The syncing works!') # LIES!

if __name__ == "__main__":
MyView(model=MyModel()).configure_traits()
```

If we instead create a `data` trait that `DelegatesTo('model')` and adjust the view to `Item('data')`, the event handler lights up. Note that the extended name syntax works insofar as properly displaying the data, just the sync traits machinery seems to be broken.

(This is on Python 3 and using a Qt backend).