multi: return txns first and last indices

In this commit we introduce first and last indices for the
tranasctions returned which can be used to seek for further
transactions in a pagination style.

Signed-off-by: Abdullahi Yunus <abdoollahikbk@gmail.com>

lntest/mock/walletcontroller.go

@@ -187,9 +187,10 @@ func (w *WalletController) ListUnspentWitness(int32, int32,
 
 // ListTransactionDetails currently returns dummy values.
 func (w *WalletController) ListTransactionDetails(int32, int32,
-	string, uint32, uint32) ([]*lnwallet.TransactionDetail, error) {
+	string, uint32, uint32) ([]*lnwallet.TransactionDetail,
+	uint64, uint64, error) {
 
-	return nil, nil
+	return nil, 0, 0, nil
 }
 
 // LeaseOutput returns the current time and a nil error.