Bug 17854: Adds print/close icon in checkout

Bug 17854: Adds print/close icon in checkout

To Test:
1) Apply Patch.
2) Go to a patron checkout screen (circulation.pl).
3) Note there are no clear screen buttons in the upper right corner of
the checkout window.
4) Turn on the DisplayClearScreenButton preference.
5) Go back to patron checkout.  Note the clear screen button and the new
printer icon next to it.
6) Click the printer icon.  This will trigger a print slip function, and
close the patron screen.
7) Try to arrow back to the previous screen.  Should go to main menu and
not the patron screen, just like the orginal close button (X).

Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>