Better charting

- Allow to plot the same day and move datepicker.
- Group by unit and add unit validation.
- Plot multiseries
- Sensors get only selected property
- Add second y-axis.
- Update search and comparison with new charting
- Add overlay and mult chan to summary boxes.
- Don't concat measurements when fetching.
Acted on @otfrom's comments.
Merge pull request #245 from MastodonC/feature/better-charting

Better and more controllable charting