Lots of rework for the Account screen

*Login Frame
 - Removed Account picker -- default account is "Savings"
 - Test account added if no login is created on the
   Create User screen

*Account Frame
 - Frame is no longer closing and reopening
 - Fixed title showing the wrong account on switch

*Create User dialog box
 - Made to be modal and not resizeable

*Accounts
 - Implemented interface and abstract classes