Fix a typo.
Avoid showing change of password form if the auth backend doesn't support it.

If an authentication backend has supports_change_password set to False, the
account preferences panel still shows the form to change the password, while it
shouldn't be there.

The problem here is that the is_visible() implementation was located in the
wrong class. Instead of being in ChangePasswordForm, it ended up in
AccountSettingsForm, so that if the auth backend didn't have the ability to
change the password, it would instead prevent the user from changing their
timezone.

Testing Done:

Before: If you use a backend that has supports_change_password as False, your
/account/preferences page still has Authentication tab, which corresponds to
password changing. If you try to change your password, you get an error as
described in the bug. You can also notice that the settings bar went missing
for some reason.

After: If supports_change_password is False for your backend, the
Authentication tab isn't visible, and the Settings tab is back!

I also verified that nothing changed for backends that support password change.

Bugs closed: 3255

Reviewed at https://reviews.reviewboard.org/r/5797/
Prevent JavaScript errors on the Manual Updates pages.

The Manual Updates page tried to load the JS catalog, needed in order to
expose gettext() for the other scripts being loaded. That path wasn't
explicitly allowed, resulting in HTML being sent back as the script
contents, causing the browser to show some errors.

We may want to consider just blocking off all script loading. That will
require blocking extensions as well, though, and possibly daeling with
other corner cases. In the meantime, allow the JS catalog to be loaded.

Reviewed at https://reviews.reviewboard.org/r/5800/
Fix the styling of titles in the admin UI.

Titles in the admin UI were previously styled by the 'h1.title' rule,
which we replaced with '.box-title'. However, the admin UI doesn't use
boxes in the same sense as the rest of the UI, due to Django's built-in
styling.

This adds an explicit rule for titles in the admin UI, allowing them
once again to use the same styles as our other boxes.

Reviewed at https://reviews.reviewboard.org/r/5801/