Changes:
- Renamed storage endpoint into dsn (data source name).
- Add additional dsn fallback property. This dsn will be used in futes
to store informations, if the main dsn backend does not work
correctly. For example, if no connection can be established over the
network to a database.
changes:
- Implement repository test for the sqlite backend
- Add testutils package to start container images
- Remove deprecated till_date in measured values
- Renamed columns of the table humidities, pressures and temperatures
