add header to all files

[nesnoj]

as in ding0 (with general info, links, authors etc.)

[gplssm]

Please use # for these file/module headers. In Ding0 we use """ """ which results in the header appearing multiple times in the automatically generated docs.

[birgits]

I would suggest the following header:

# This file is part of eDisGo. Copyright belongs to
# Reiner Lemoine Institut gGmbH, authors are recorded in the version control
# history of the file, available from its original location on github:
# https://github.com/openego/eDisGo/.
# SPDX-License-Identifier: AGPL-3.0-or-later
#
# eDisGo stands for Electrical DIstribution Grid Optimization. It is a python 
# package for analysing different flexibility options in distribution grids.
# eDisGo is developed on github: https://github.com/openego/eDisGo/, the
# documentation is available on RTD: https://edisgo.readthedocs.io.

It is a mix of the header suggested by oemof and the one ding0 uses. What I like better here is that authors are not directly named. Instead it is referred to github, which results in not having to update the header everytime someone new contributed. @nesnoj and @Ludee what do you think?

[nesnoj]

Like it 👍