Remove speakers / themes
Issue #141
new
The "edit themes / speakers" form still have no deletion of those items; the button for speakers is missing and the one for tags is not working.
Both should be implemented using a second field to do ID diffs: we create a field with the current values, the other field gets filled as it is now, and in the server we diff the two arrays: what's not in the second gets removed and what's not in the first gets added.