Allow entering minimum payment as a percent

[zachborboa]

Minimum payments can be a percentage of the balance. Thus the tool should allow entering a percentage as well as using a minimum amount and choose the greater of the two as the minimum payment.

Fox example, a balance of $2,230 and a minimum payment of the greater of $25 or 2%:
$2,230 * .02 = round( $44.60 ) => $45.00
Minimum payment would be $45 and not $25.