Provide documentation of how to set up a deployment

[UsualSpec]

Currently https://github.com/nsg-ethz/autopower/tree/main/client#autopower-client only shows how to set up an Autopower device. However, this does not document how an actual deployment in the wild would look like.

I'd suggest to also document this even though it's simple. My suggestions:

1. Document a setup device should be checked for obvious defects (soft and hardware): Check if device boots up, registers and gives data. Potentially delete measurements from the DB on the autopower device (login data for the local DB is in /etc/mmclient/secrets.json. Deleting measurements works very comparably to https://github.com/nsg-ethz/autopower/blob/main/server/USING-POSTGRES.md#maintenance-and-deletion-of-measurementsclients on the server side), check if there are any new errors showing in monitoring
2. Set up a run in the Management UI with the respective DUTs. Power down the Pi.
3. Send/deploy hardware at DUT
4. Check after some time if the devices registered correctly on the server.