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
Use buffers and filter out sensors w/o data.
Merge pull request #289 from MastodonC/feature/fix-channels

Use buffers and filter out sensors w/o data.
Fix editable on parse-entities.
Update can-add-* based on history

In addition to fetching. We don't fetch at the right level to update
can-add-* only when we are fetching.
Removed unneeded logging.