Password autocompletion

When having saved the profile page with a browser remembering passwords, and agreeing to do so afterwards, and visiting the profile page again, only one of the two password fields in filled in. This means that the user needs to enter his password, or remove the existing one. This pull request disables autocompletion on password fields in the profile page. And adds a workaround for Firefox. Also useful for admins editing other users' preferences.

The order of fields is also changed, so that when browsers still offer to store passwords uses the correct username field (which must be just before the first password field).