Calculate Only Unique Repayment Methods

[Zoramite]

When calculating the schedules for repaying debts there are currently 6 different methods for repaying the debt. Currently they are just different ways of sorting the debts (ex: highest rate first) and the sort order is cacheable.

When working to compare different repayment methods we need to eliminate the duplicate sort orders so they are not recalculated multiple times.

Also the winning method should be the least complex method. For example, if the highest rate first and the balance-to-payment ratio methods use the same sort order then the highest rate first should be chosen since it is conceptually easier to understand.