Add form validation on the client side

I haven't had a chance to implement everything on the server side yet.

This makes it so that you can only submit the form once media has been upload and the required fields are filled in.  Note there is an error causing some of the validation to not work: https://github.com/unl/wdntemplates/issues/816

#123
I don't believe `enable()` is a jQuery method. I think you have to use `prop('disabled', false)`