[#72676850] inventory_pool checkboxes

Squashed commit of the following:

commit 7b504d2676451b2e7be783bbf09d798c8899ea70
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Tue Jun 24 00:56:32 2014 +0200

    tests for checkboxes

commit daefae10f8f33b2596fbb7c988127562564284f1
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Sat Jun 21 19:40:50 2014 +0200

    autocomplete on hand_over should only find models matching items inventory_pool_id to be set to the current_inventory_pool

commit 851f2056967abb181ac0fa447791a11279f6b990
Author: Franco Sellitto <franco.sellitto@zhdk.ch>
Date:   Sat Jun 21 19:29:47 2014 +0200

    fall back for deactivated checkboxes (same trick used by the checkbox_for rails helper)