Provide more detailled documentation for server installation

[UsualSpec]

Currently https://github.com/nsg-ethz/autopower/blob/main/server/README.md is not detailled. We should improve server documentation by setting up a server on a VM.

This is for reproducability.
Probably, this is low prio for now...

[UsualSpec]

Worked on this while setting up the test server. It's not yet "nice", but should be a bit more detailed as before.