Support the labelling of data per measurement campaign

[rouvoy]

We would like to split the uploaded data into separate databases depending on the measurement campaign. Therefore, it would be good to add a setting in the mobile app to indicate the measurement campaign to which the user is going to contribute.

Ideally, one should be able to query the datastore to list the available databases that one user can contribute to. If no API is available for listing the databases, one can leave a single string and create the remote database if none exists.