Add docs about using as alternative to 'stata_setup' package

[hugetim]

Add something about this to the User Guide, and maybe also about other 'nbstata` utilities that may be helpful when working in a Python notebook:

When you want to use Stata within a Python notebook (as opposed to a Stata notebook), 'nbstata' provides a convenient way to load Stata so that the %%stata magic will work. For most users (when a config file is not needed to locate the Stata directory), the following lines will do it:

import nbstata
nbstata.launch_stata()

Compare Method 1 in the official pystata docs. (All the methods suggested by Stata require you to type out the Stata directory and edition in the code to initialize pystata.)

[hugetim]

Other 'nbstata' utilities of potential interest to pystata users:

• nbstata.pandas.better_pdataframe_from_data - improves on pystata.stata.pdataframe_from_data by making the pandas DataFrame index correspond to Stata observation numbers and also providing an option to output numeric values as strings using their Stata formats.
• nbstata.stata_more.diverted_stata_output - returns the output of arbitrary Stata code as a Python string (without affecting the Stata state)