REFACTOR
Merge branch 'master' of github.com:BCS-io/letting
FEATURE import accounts
ImportAccount now handles the basic reading of rows and applying credits and debits to the related account.
AccountRow - wraps csv row object - help with the credit /debit behaviour differences
calculates amount it can set in a credit through CreditableAmount
Merge branch 'master' of github.com:BCS-io/letting