Replace divs with Dough form helpers
Add form validation summary and error fields
Resolves issue with fragile matching
Merge pull request #37 from moneyadviceservice/add-dough-form-helpers

Replace divs with Dough form helpers
Adds validation feature
Simplifies `.authenticate`
Ensures uniqueness of FCA numbers for Principals

* Reworks factory callbacks to run on `build` and `create`
Adds validation per the story comments

* Some fields are 'approximately' valid
* Needed to clarify web address validation so left this out for now
Reworks to use SitePrism's `elements`