Prevent order setting vs. form submission race condition

If the js runs slow for any reason the admin form can submit before the order of inlines has been set.
Fix typo
Create new model field OrderField
OrderWidget.is_hidden should evaluate False
Update orderable ordering to use the submit event

It seems that the click event may not be guaranteed to run in FireFox before the form actually submits.  This may be due to a variety of factors including the version of jQuery but for now switching to the submit event solves the problem.
Added Sean Hussey to AUTHORS.
Merge
Merge
Merge