Description

This PR fixes some of the remaining Sphinx errors and warnings coming out the Python/website part of docs generation. It fixes some Scala-related docs errors too.

🐞 get_constant ambiguous reference - fixed this Sphinx error; interesting note that text right after the Returns line is expected to be an entity so you have to make sure the reference is good and unambiguous.
🐞 Scala docs used interpreter examples, but the current jar doesn't work with the interpreter, so I removed this notion from the index, ndarray, kvstore, and symbol pages. kvstore and ndarray also had Sphinx errors, which are fixed now.
🐞 The gluon index page had parsing errors. I think it is because the python code on that page isn't really functional and Sphinx was running it and failing. So I removed the python declarations. A gluon expert should really take a look and see what that page needs as far as an update with the latest/greatest info...
🐞 ubuntu setup - I already updated the pip package graphic, so this old table was not needed... and it was causing a Sphinx warning, so I removed it.
🐞 r tutorial fix - this had {r} on one of the code blocks... Sphinx/Pygments didn't like it, so I removed the braces.