Fixed bug with js variable naming and Firefox regression

Firefox doesn't use toElement in the dragevent. Fortunately, both chrome
and firefox uses target to fill the value of the element. Also fixed
issue with naming of variable. Some caching apparently made the thing
working when it shouldn't.
Need an update view for when post update fails

This is similar to create.html.erb where it's only called when there's
an error. Maybe I should rename both to error.html and return them but
it gives an extra condition in the controller which can become
cumbersome.

Maybe a after callback could check for the record and render error...