Adapt processing of evaluated period

[MaGering]

With this PR it is possible to run simulations over a time period that is shorter than a day. This can be handy in order to study the calculations stored in the lp file.

The following steps were realized, as well (if applies):
❌ Use in-line comments to explain your code
❌ Write docstrings to your code
❌ For new functionalities: Explain in readthedocs
❌ Write test(s) for your new patch of code

• Update the CHANGELOG.md (let's start this after the first release)
• Apply black (black . --exclude docs/)
• Check if full simulation tests pass locally (EXECUTE_TESTS_ON=master pytest)

Please mark above checkboxes as following:

• Open
• Done

❌ Check not applicable to this PR

_{For more information on how to contribute check the CONTRIBUTING.md.}

[SabineHaas]

Nice 👍

I think we should use the checkboxes from now on - at least ticking the ones that can be applied to the PR. So before merging please fill in the changelog and run the test.