Pages that don’t have navigation shouldn’t extend the top-level admin
template directly.
They should extend `withoutnav_template.html` instead, because then they
get a wrapping `<main>` element, which is good semantically and for
accessibility, and also defaults the font size to `19px`.
This commit adds a page or series of pages for changing your:
Name | Email address | Mobile number | Password
------------------|-------------------|-------------------|------------
Enter new value | Enter new value | Enter new value | Enter new value
| Enter 2fa code | Enter 2fa code |
Return to profile | Return to profile | Return to profile | Return to profile
(each row is a page)