Ability to see existing ref nos when adding a new resource

In v 8.0.34 and above there is now a popover button to the window you see when entering or editing a reference number for a resource. (The window they see when they click the pencil next to the 'Ref No' field.)

​It's a yellow button labelled "Show existing ref nos." When clicked, it displays a portal that users can scroll down to view all reference numbers already in the system. Hopefully it will help them know what number they're up to! Reference numbers are sorted alphabetically in the portal. (Remember, 'Ref no' is a TEXT field so if numbers are used in this field they are sorted alphabetically rather than numerically i. e. 1...10..100...2...3.. etc)