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.

signup.go

@@ -107,6 +107,7 @@ type AcctInfo struct {
 type AcctInfoResponse struct {
 	XMLName  xml.Name   `xml:"ACCTINFOTRNRS"`
 	TrnUID   UID        `xml:"TRNUID"`
+	Status   Status     `xml:"STATUS"`
 	DtAcctUp Date       `xml:"ACCTINFORS>DTACCTUP"`
 	AcctInfo []AcctInfo `xml:"ACCTINFORS>ACCTINFO,omitempty"`
 }