API proposal: shoudn't the "index" property (and parameter) of a df renamed "rows" ?
Sorry to open a issue for such a minor thing..
in a DataFrame object, both the `columns` and `index` properties are actually `Index` objects.
Wouldn't be cleaner to rename `index` as `rows` ?
As you are working with n-dimensional panels, `rows`  and `columns` could then be just convenient aliases for something like `axis0` and `axis1` respectively (in a df), while further dimensional container could use `axis2`, `axis3` and so on (the current axis names `labels`, `items`, `major_axis` and `minor_axis` do not suggest any particular order).
