Add inplace option to many DataFrame, etc. methods

[wesm]

On larger datasets methods like

• sort_index
• rename

(add methods to list)

etc. would benefit from an inplace option, e.g.:

df.sort_index(by=col, inplace=True)

and this would be more memory efficient

[wesm]

@changhiskhan I think if we do rename and sort_index, we should be good to go for now. It will be an ongoing effort to add in-place options to methods, too much for a single issue probably...

[changhiskhan]

ok, cool. rename is there. I just have to do sort_index