Bug 29458: Reorder login elements

Bug 29458: Reorder login elements

Make masthead.inc modal and opac-auth follow the order of the login
elements on the homepage.

Test plan:
Enable prefs for reset password and self registration.
Fill additional contents for login instructions.
Logout on OPAC.
Click Login from your account on top bar.
Click Login button on the home page (right side, in the middle).
Verify that these two forms correspond with the home page login.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Bug 29458: (follow-up) Remove FIXME

With some help of Owen Leonard:
<oleonard> Regarding the <br/>, you can wrap the submit button in <fieldset class="action"></fieldset> instead.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>