radio/select/checkbox options are now drag-and-drop sortable. good
candidate for merging back into non-reason-specific versions.
(partial) fix for https://app.asana.com/0/691627771928/9496431081337
fix for firefox dragging bug. Especially when edit interface is up in
fb-left, it was possible in Firefox when reordering elements on the
fb-right div, for the element to pop over and start overlapping the left
frame. This fixes that. Addresses
https://app.asana.com/0/691627771928/9515041912172 "Fix Firefox dragging
bug"