Feature tax service tests remove taxes from all order items tests

-Added tests for the TaxService function addTaxAddressesStructBillingAddressKey()
-Added tests for the TaxService function removeTaxesFromAllOrderItemsTests()
-Cleaned up removeTaxesFromAllOrderItemsTests() in TaxService
-Address comments in the previous/closed pull requests
-Merged in develop branch with recent changes made by Greg