sort *all* GetSignBytes:

- call MustSortJSON before return JSON bytes to guarantee alphabetic
ordering

- moved SortJSON and MustSortJSON to types package to avoid cyclic
package dep

types/utils.go

@@ -0,0 +1,31 @@
+package types
+
+import "encoding/json"
+
+// SortedJSON takes any JSON and returns it sorted by keys. Also, all white-spaces
+// are removed.
+// This method can be used to canonicalize JSON to be returned by GetSignBytes,
+// e.g. for the ledger integration.
+// If the passed JSON isn't valid it will return an error.
+func SortJSON(toSortJSON []byte) ([]byte, error) {
+	var c interface{}
+	err := json.Unmarshal(toSortJSON, &c)
+	if err != nil {
+		return nil, err
+	}
+	js, err := json.Marshal(c)
+	if err != nil {
+		return nil, err
+	}
+	return js, nil
+}
+
+// MustSortJSON is like SortJSON but panic if an error occurs, e.g., if
+// the passed JSON isn't valid.
+func MustSortJSON(toSortJSON []byte) []byte {
+	js, err := SortJSON(toSortJSON)
+	if err != nil {
+		panic(err)
+	}
+	return js
+}