Remove the model-service table

[albertsgarde]

It is not necessary to explicitly store which services are available for which models.
Instead, this can be calculated from which data objects a model has available.
To do this, each service provider must provide a list of necessary data objects.
When receiving a service API call, first check that the model has the necessary data objects, and if not, respond with an error message saying which are missing.
When receiving an all API call, the response JSON should contain an object for all services in the database, with the before mentioned error message for the unavailable ones.