Bug 26160: Make POS items table configurable

Bug 26160: Make POS items table configurable

1)  System preference:  EnablePointOfSale - set to Enable
2)  System preference:  UseCashRegisters - set to Use
3)  Administration > Accounting > Cash registers - create a new cash register for the library you're logged in as
4)  Administration > Accounting > Debit types - create at least one debit type
5)  Home > Point of sale - verify that all four columns exist in the Items for purchase table:  Code, Description, Cost, Action
6)  Administration > Additional parameters > Table settings > Point of sale - change which columns can be hidden and/or toggled
7)  Home > Point of sale - verify that your choices have been implemented (columns are hidden, columns can be toggled, columns can't be toggled)
8) Repeat steps 6 and 7 for different combinations, checking that they all work.

Signed-off-by: Sally <sally.healey@cheshiresharedservices.gov.uk>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Added Sally's test plan.

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>