Fix credit_account & debit_account Methods in Salary Model
Fix credit_account & debit_account Methods in Salary Model

- no use of tags yet, but same interface as the new invoice model in bookyt > 2.0
silvermind/bookyt_salary,huerlisi/bookyt_salary,silvermind/bookyt_salary,silvermind/bookyt_salary,huerlisi/bookyt_salary,huerlisi/bookyt_salary