Loans and Repay

GMS now has the ability to track grain loans and repayments with two new transaction types. When activated elevators can loan grain to producers and notify the operator of the debts whenever the producer returns. Producer debts MUST be repaid before any other grains can be stored or bought. Loans are tracked in a similar fashion to customer storage. Future and elevator positions can also be calculated including (or not) grain that is on loan. Loan and repayments are sent over to accounting as expected.