Add todos
Added LegacyUserCharge import
Updated todo
Added LegacyMortgagePayment import
Added csv export to ignore file
Added MortgagePayments to master import task
Remove tmp file created for test
Added LegacyUserBalance import

The old system did not have a separate table for balance.
A virtual legacy model was created to deal with the import.
The balance calculation code was taken from the old system.
Added comments to explain where the code came from.