Bug 26478: Display issue with buttons on the self checkout screens

Bug 26478: Display issue with buttons on the self checkout screens

This patch adds missing Bootstrap classes to a few buttons on the self
checkout page. Without the classes the buttons are not styled correctly.

To test, apply the patch and open the self checkout page for a patron
with multiple checkouts, some renewable and some non-renewable.

In the table of the user's checkouts the "Renew item" button should be
styled as a green button. The "Check in item" button should be styled as
a blue button.

Try to check out an item which cannot be circulated. On the page warning
you "Item cannot be checked out," the "Return to account summary" button
should be styled as a blue button.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>