Documentation fixes

[mure]

• [x] This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• Properly documents methods of DataFrameClient The uplink decorators turns the functions into objects and Sphinx isn't auto documenting them meaningfully, even though the special methods like __doc__ are preserved. After some trial and error, I discovered that manually specifying the methods with automethod:: gets Sphinx to treat the objects like functions and generate the correct docs.

• Reduces the clutter on the index page by reducing the TOC depth

Why should this Pull Request be merged?

It makes the docs better!

What testing has been done?

• See the built docs from this PR

[cameronwaterman]

Whoops - forgot the "docs:" tag in the title. Shouldn't matter as it doesn't produce a new release for docs I don't think.