Better chart updating.

Through the use of IDidUpdate. Thx @annapawlicka !
Merge pull request #472 from MastodonC/feature/better-chart-updating

Better chart updating.
Introduce sensor_id.

- Update calculations.
- Store sensor_id in datasets.
- Update datasets API and UI to support sensor_id.
- Make dataset name editable.
- Update uploads and downloads with sensor_id.
- Update measurements API to support sensor_id.
- Update devices API.