== Granular control over how to use price and acquisition cost to determine item value  ==

This feature adds two new library settings:

    Use Item Price or Cost as Primary Item Value
    Use Item Price or Cost as Backup Item Value

which intersect the behavior of these existing settings:

    Charge lost on zero
    Default Item Price
    Minimum Item Price
    Maximum Item Price

Each of these settings affect how item price is used in
various contexts and is not limited to "lost" items, but
can affect notices, fine rules, and billings for long
overdue and damaged items (as well as lost items).

By default, the price field on items is the only field
considered by these various uses, but if we set, for
example, "Use Item Price or Cost as Primary Item Value" to
"cost", then we'll use the cost field instead of the price
field.

Alternately, if we set the "Backup Item Value" to "cost"
and either leave the "Primary Item Value" setting unset or
set to "price", then we'll consider the price field first,
and if it is either unset/null or equal to 0 (and
"Charge lost on zero" is true), then it'll fall-through to
the cost field.  We can also flip the behavior with these
settings and consider cost first and then price second.

The primary intended use case for this feature is:

 If there's an acquisition cost, charge this as the lost value.
 If there's not an acquisition cost, but there's price, charge the price.
 If neither, charge the default value.