* Refactored the parameters for DBGetPayments and added default values
* Added GetPayments to Sales
* Added non-zero default values to Payment
* Added PaymentId code to DatabaseManagerCustomers
* TODO: Either Customer table's zipcode column needs to corrected to be a string, not an integer, or the Customer class' ZipCode needs to be an integer and the UI needs to format the display value with 0's for low ZIPs
* Added a list of abbreviated state names for use in Customer's State
* Finished EnterEditInventoryForm code I missed in the last commit
* Added GetEmployees to Employee class
* SearchCustomersDialog should be now fully working
* EnterEditCustomerFrom is almost finished, except for the payment bits, and the data layer's issue with ZipCode mentioned earlier