Bug 7953 - add opacuserjs to the sco template

Bug 7953 - add opacuserjs to the sco template

To test:
add some jquery to opacuserjs that would change the screen
a la: $(".checkout label[for='patronid']").css("border","3px solid red");
verify you see a red box on the sco-main page.

Also adds the ability to use opacusercss to style sco-main.tt

to test:
Add some css to opacusercss that would change the screen:
.checkout { background: grey; }
verify you see a grey box around the checkout div.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
http://bugs.koha-community.org/show_bug.cgi?id=7959
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>