This updates the styling and templates for the page to leverage the new

CSS component classes for the form and the confirmation prompts,

finishing up the presentation of this page.
The form and fieldsets now match the new admin UI style, and the

fieldsets are injected via a specialization of the main fieldset

template.
The confirmation prompts and SSH key info now live in rb-c-alert

components, with new admin-specific CSS component classes for the SSH

key and certificate information.

Tested all the various confirmation prompts for the form, including

buttons when shown.
Tested creating plain and service-backed repositories.
Tested with and without SSH keys on the system.