Modify the ESS CSC to support data clients which communicate with sensor data servers. This will allow different kinds of remote sensors, including those connected to a LabJack, but this ticket just adds a base client and an RPi client; adding a LabJack data client will be done on a different ticket.
- Add BaseDataClient, MockDataClient, register_data_client_class and get_data_client_class to ts_ess_common. Putting it here instead of ts_ess_csc avoids circular dependencies for future data clients such as the LabJack client. Each data client has its own config schema.
- Add RPiDataClient to ts_ess_csc.
- Update the CSC config schema to support data clients.
- Update the CSC config schema to put data for all ESS instances in the same data file. The CSC picks the correct piece of configuration based on its SAL index.
- Update the config schema version from v1 to v2.
- Add an ESS/v2 directory to ts_config_ocs, with a single file "default.yaml" that contains configuration for all existing ESS instances.