Add schema validation to measurements API.
Merge pull request #80 from MastodonC/feature/measurements-fix

Add schema validation to measurements API.
Editable devices

- Don't select row when it's being edited.
- Add checkbox for creating calculating fields.
- Add allowed?* for devices.
- Use chart's date format.
- Make table scrollable (when the screen is too small to allow for
  required min table width)
- Don't use min library for development. Hide divs instead of removing them.