Add trust commerce dependency.
Add trust commerce request,response fields and values.
Add TrustCommercePaymentProcess to processCreditCardTransaction(...)
Add TrustCommerceException.
Add TrustCommercePaymentProcessTest
Simplify exception handling.
Refactor to more readable enumerated type names
Get non null trust commerce properties
Add PaymentProcess interface and implement in Payment processes.
Refactor conference costs payment gateway credential field names
In preparation for introducing another payment gateway type
Establish PaymentGatewayType
Refactor (in the code) authnetTransactionId to simply transactionId
Change authnet_transaction_id to transaction_id at the database layer.
Add PaymentGateway to Conference and ConferenceCostsEntity
Refactor TrustCommerce processCreditCardTransaction
Add support to TrustCommercePaymentProcess for credit card refund.
Add test of TrustCommercePaymentProcess credit card refund.
Simplify PaymentGatewayType
Add payment gateway type to conference costs table
Add payment gateway type to conference costs service layer