Bug 21297: Display public lists to existing lists when adding a new item

Bug 21297: Display public lists to existing lists when adding a new item

If there are no private lists the public lists are not displayed.

Test plan:
1) Add 10 public lists (This is when the 'More lists' menu item becomes
view-able)
2) Select an item
3) Click Add to list
4) Select 'More Lists' menu item
5) Note that 'Select an existing list' is an available option

Signed-off-by: Caroline Cyr La Rose <caroline.cyr-la-rose@inlibro.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>