This fixes one of the issues in #4351 where the radio button was not
selected. This was likely introduced during the upgrade to d3 v4, now
that enter selections do not automatically flow into update anymore.
(the fix is to add a `merge` to ensure that the `selection.each` actually
has some things to iterate over)
- Attempt fast save first, only perform conflict resolution if necessary (re: #3056)
- Block reentry of save, and dont keep focus on save button (closes#4641)
- Refactor modeSave() for code clarity (avoid shared state in closure variables)
