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
Interesting.  I used it because my IDE suggested it, and it is indeed enabling the submit button.  I am very curious where it is defined and how it should be used now.