Better datetimepicker

- Use local state for datetimepicker component.
- Add +/- boxes
Act on @otfrom's comments.
Merge pull request #437 from MastodonC/feature/better-datepicker

Better date picker
Guard against nil mode.
Merge pull request #439 from MastodonC/feature/resolution-fix

Guard against nil mode.
Improve clearing of properties cursor.