Rewrite patient registration using Angular for form validation

[jniles]

Angular's built-in form validation is awesome, and we should be using it more. A significant enhancement would be to apply form validation to the large patient registration form. The goal would be:

1. Allow the user to click the submit button on an invalid form, to show error messages around fields that have missing or invalid values
2. Custom error messages for all fields, such as "this data is required" or "date of birth must be within xxxx -- yyyy".
3. Disable the form while it is being submitted to the server.

This would significantly clean up our client code, and allow the controller to deal with logic instead of validation. It also would enhance the user experience significantly.