Bug 27631: Changed <h1> around logo to <div>

Bug 27631: Changed <h1> around logo to <div>

To test:
1) Look at Staff Client and the logo
2) Apply patch
3) Check Koha logo moves to the middle of the page when zooming in
4) Ensure page source shows logo inside <div> and not <h1>

Sponsored-by: Catalyst IT
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>