Store key origin info in key metadata

Store the master key fingerprint and derivation path in the
key metadata. hdKeypath is kept to indicate the seed and for
backwards compatibility, but all key derivation path output
uses the key origin info instead of hdKeypath.

src/script/sign.h

@@ -22,13 +22,27 @@ struct CMutableTransaction;
 
 struct KeyOriginInfo
 {
-    unsigned char fingerprint[4];
+    unsigned char fingerprint[4]; //!< First 32 bits of the Hash160 of the public key at the root of the path
     std::vector<uint32_t> path;
 
     friend bool operator==(const KeyOriginInfo& a, const KeyOriginInfo& b)
     {
         return std::equal(std::begin(a.fingerprint), std::end(a.fingerprint), std::begin(b.fingerprint)) && a.path == b.path;
     }
+
+    ADD_SERIALIZE_METHODS;
+    template <typename Stream, typename Operation>
+    inline void SerializationOp(Stream& s, Operation ser_action)
+    {
+        READWRITE(fingerprint);
+        READWRITE(path);
+    }
+
+    void clear()
+    {
+        memset(fingerprint, 0, 4);
+        path.clear();
+    }
 };
 
 /** An interface to be implemented by keystores that support signing. */