breakdown account service

Split account service into a user account and a DDA - Demand Debit Account Service. The user account is responsible for the user information (id, name, address, password, etc). The DDA is responsible for keeping track of the transactions on the account (i.e. debits and credits) and overall balance.

Also, the password should be split out from the "account" object and stored safely, i.e. a salted.
