Docstrings in DoppelGANger

[loehndorf]

First of all. Thanks for the great work. I was able to use it to generate time series of natural inflows into water reservoirs, and it worked without much changes to the code.

It took me a while to figure out the right format though. I would have been much faster if the DoppelGANger class had proper Docstrings. I pretty much had to guess and try how the functions other than the constructor work. Providing some simple examples would also help.

[fjxmlzn]

Glad to hear that it works for your application, and thanks for your suggestions!

We provided some simple examples in "example_*" folders. I will add more detailed docstrings and examples to the repo.