Re-do structure population

[nhoening]

The flexmeasures add structure command basically is an opinionated take at what structure should be on a (fresh) FM server.

I get that we want some default GenericAssetType instances to be there. So that is what this could become - default types. I'm open to adapt the name, as well if that is the case.

[Flix6x]

Perhaps flexmeasures add example, which creates an example organisation, a few user accounts, a few asset types and assets with sensors, and optionally some time series data, too?

[nhoening]

Also, some basic roles. For users, admin, for accounts, Prosumer, MDC etcetera

[nhoening]

@Flix6x The example idea should be another ticket, I think.

[Flix6x]

The example idea should be another ticket, I think.

Okay, I get that. I made #340.

[nhoening]

Solved by #349