Initial customer methods on IInvoiceService and IPaymentService
Adds customer payment methods and extension methods off ICustomer to more easily expose associated invoices and payments
Associates a customer with an Invoice on during the sales workflow.
Blind attempt at fixing the decimal issue - can't look up the issue # atm.
Initial work on the CustomerApiController and customer display models
Housekeeping
#M-296 Fixed
Merge pull request #712 from rustyswayne/1.3.0

Customer extensions, started CustomerApiController and refactored PutShipMethod on ShippingApiController