Add two new classes for form validation
Add two new classes for form validation

.form-group-error - to apply a red border to a .form-group
.fom-control-error - to apply a red border to a .form-control

This removes the need to set a parent ‘.error’ class - at present this
is setting both a border to the left of a form-group div and the border
on a form control.

alphagov/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements,alphagov/govuk_elements