set deductible amount at the price field option level

when creating a new contribution, we have the ability to set the non-deductible amount (and thus by difference, the deductible amount). however, often times orgs need the ability to set those amount via price sets at the option level – and have that calculate out to the contribution record.

it appears this functionality was envisioned when the price set schema was developed. currently the civicrm_price_field_value table includes a field for storing the deductible_amount, though that is no where exposed to the interface.

1. decide if we retain the structure as-is or bring the contribution record and price_field_value record into alignment (the contribution stores the non-deductible amount; the price field option stores the deductible amount)
2. expose the deductible_amount field to the price set option form
3. when line_items are selected, transfer the calculated configured deductible amount to the line_item record
4. when the line items are summed to determine the contribution's total_amount, also determine the total deductible amount and store in the contrib record
5. include that field in appropriate reports and make sure it is available for exporting