Show choice text on normal type tooltips, not date (fix #28).
clean up date/time selection (fix #25)
Poll deletion
implement feature: comment per vote (close #33)
Add day poll type (close #23)

* convert Enums to VARCHAR, required for migration :(
* improve grouping of choices, allow "path-style" choice texts for
  grouping
* choice selection does not reenable previously disabled choices (fix #12)
Fix grouping errors by checking if grouping works