Implement auto-update function

[ClaraBuettner]

Here is the branch with the changes we did together today in the morning: https://github.com/openego/powerd-data/tree/features/auto-update-function

@ulfmueller @isGut Please feel free to update the description of this issue :)

Okay, here is an overview of the tasks identified so far:

• [ ] #143
• [ ] #144
• [ ] #145
• [ ] #146
• [ ] #147
• [ ] #148
• [ ] #149
• [ ] #150
• [ ] #151
• [ ] #152
• [ ] #153
• [ ] #154
• [ ] #51
• [ ] #155