better hover handling for list rows

sometimes, simply toggling gets confused
Re-use existing rows when reloading

This allows us to keep the focus and not have to interrupt running
effects on this row element. Also, it seems cleaner. Not to mention
less memory-hungry.
Automatically reload rows after dnd’s

This fixes most of the problems described in #153.
I’d classify the remaining problem (clearing tags in the detail and then not reloading)
as WONTFIX as it’s too littl gain for so much effort.