Documentation Feature Request: Rolling and Coordinates

The documentation about iteration with rolling contains the following:

We can also manually iterate through Rolling objects:

for label, arr_window in r:
   # arr_window is a view of x

It would help to explain what sort of thing label is, and how we can use it. It seems to be an object of type Coordinate, but Coordinate does not appear in the API reference.

So I would suggest the two following improvements:

1. Add an example of using the label and arr_window, maybe plotting the arr_window with the label used to give title.
2. Tweak the document generator to include docstrings from Coordinate in the API reference section.
3. Crossreference (hyperlink) from this section of the doc text to the API reference.

Locate the documentation section describing iteration over Rolling objects, the document generator, and the Coordinate API documentation. First inspect how rolling examples and API-reference entries are generated; done means the example explains label and arr_window, Coordinate docstrings appear in the API reference, and the rolling section links to it.