Bug 17845: Remove unused code related to printers

Bug 17845: Remove unused code related to printers

There is some quite old and unused code in Koha related
to printer configuration and network printing. These code
hasn't been functional in a long time and should be removed.

This patch:

- Removes printcirculationslips system preference
- Removes table printers
- Removes branchprinter column from branches

Check that:
- Go to administration
- Open any age there, but change the last bit to: printers.pl
- Apply patch, run the database update
- Verify the hidden page no longer exists
- Verify that logging in and out still works correctly
- Verify that checkout and returns work correctly
- Switch to another branch using the "Set library" option

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>