Update docstrings for new functions

[nsryan2]

Some functions, like set_distribution in commodity.py or add_regional_data in technology.py have increased capability due to new arguments, and need to have their parameters and returns updated.

We are following the numpy style of docstrings, so please add the components inputs, returns, and descriptions.

If you are unsure what a function does, feel free to ask!

Edit: This isn't a comprehensive list, but there are also some in db_creator.py like create_lifetime_tech