Add ThermoLog skeleton class.

- Define ThermoLog class.  Currently it is an empty class as we know
  we need a model for it but don't know what it should look like yet.
- Minor cleanup of the core Flow class.
Use built-in log level messaging to log debug message if debug is enabled.
Minor lint cleanup of lint warnings.

- Use string references for i18n compatibility.
- Add contentDescription to ImageView
Remove non-existent service from android manifest