Add ipython tab autocompletions for TsdFrame columns

[eschombu]

Using this stackoverflow answer, we can get the behavior shown in the screenshot.

[gviejo]

I am curious what it does when you don't have strings for columns

[gviejo]

Ok I am not sure it's a good idea if you don't have labeled columns. It does this for integers but it's a bit misleading because this is numpy behavior now

[eschombu]

I guess I haven't used pynapple enough to have realized the various kinds of objects that will use the TsdFrame.getitem method, and keys used by that. I could definitely add some sort of check to only show columns labels if they're all strings. Or we can drop the idea.

[gviejo]

I would drop it because I would like eventually to force the behavior of slicing TsdFrame with the .loc when there are labelled columns. That would disambiguiate many things.