Bug 16511: Making contracts actions buttons

Bug 16511: Making contracts actions buttons

To test:
1) Go to Acqui -> find a vendor
2) On Vendor details page (supplier.pl) confirm that Contracts table now
   has one column called Actions
3) Confirm that Edit and Delete show as buttons
4) Confirm that buttons don't wrap on a narrower browser
5) Click Contracts tab
6) Confirm Actions column, Edit and Delete buttons, and button's don't
   wrap

Sponsored-by: Catalyst IT
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan Gallagher <brendan@bywatersolutions.com>