Edit attributes with lists and dicts

[nhoening]

We have the flexmeasures edit attribute CLI command.

It allows to edit attribute values of several types on assets and sensors: float, bool, str, int.

(attributes are where we store things that are not ready (yet) to become engrained in our database model of assets and sensors. Often, this is about dev features.

Now we are handling lists as attribute values, as well (e.g. generic_asset.sensors_to_show), and are thinking about dictionaries.

This issue is about supporting these two types in the CLI command, as well.