Add client-side validation to the definition forms

[adam-werner]

In the Site Definition, Action Definition and Export Type Definition forms, submissions without field entries can result in an error.

Site Definition Form

Action Definition Form

Export Type Definition

Possible solution approach

With some angularjs controller updates, form validation can be incorporated there. Alternatively, the corresponding API endpoints being called by the angularjs controllers can return validation messaging errors.

[Mulliman]

xStatic 14 now has much better validation with the UUI refactor.