Include clustering for selecting of representative days

[simnh]

I added a feature branch where I pushed 'a proof of concept' . I should generally work, but there mights still be bugs and at some point, we should definitely clean that up its really just hacked in there

branch is: features/clustering

[gplssm]

Don't worry about your hacking too much as the structure of the package in quite weak in general. Once, we have clarification about repositories in the open_eGo project and its interdependencies, we can refactor structure of code in the repo.

[mariusves]

I think this can be closed, am I right?