Revise invoicing to provide line-item amounts in db tables sent to DCYF

[gregorp]

To provide more easily audited account information, OIAA has requested that dollar amounts get added to line items in the billing tables.

This will entail:

• Revising invoicing logic to compute dollar amounts per line item and then sum them (rather than the current: sum items and then compute dollar amounts).
• Carefully testing equivalency with old invoicing logic (up to some potential rounding errors)
• Including these amounts in the billing tables in the DCYF schema sent to OIAA
• Documenting the new fields in the data dictionary