Bug 23772: Revert to passing itemtype objects to the template

Bug 23772: Revert to passing itemtype objects to the template

This patch restores the methodology prior to bug 23602 of passing the
full Koha::ItemType objects to the template and thus giving us the
ability to use all the methods present within them.

Test plan:
1) Ensure you have at least one itemtype with an assigned icon and the
   images enabled.
2) View the itemtypes admin page and note the icons display again
3) Ensure you have at least one itemtype with library limitations
   defined.
4) View the itemtypes admin page and note the library limitations still
   display.
5) Signoff

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>