Add test for banking responses

This also adds a generic response equality testing framework, a missing
Status field to all current responses, and Equal() methods to all basic
types.

banking.go

@@ -126,6 +126,7 @@ type Balance struct {
 type StatementResponse struct {
 	XMLName       xml.Name                `xml:"STMTTRNRS"`
 	TrnUID        UID                     `xml:"TRNUID"`
+	Status        Status                  `xml:"STATUS"`
 	CurDef        String                  `xml:"STMTRS>CURDEF"`
 	BankAcctFrom  BankAcct                `xml:"STMTRS>BANKACCTFROM"`
 	BankTranList  *TransactionList        `xml:"STMTRS>BANKTRANLIST,omitempty"`