Flesh out membership certificate with signature, better serialize/deserialize, and rename parameter to qualifier to make better conceptual sense.

node/Address.hpp

@@ -231,6 +231,15 @@ public:
 	 */
 	inline operator bool() const throw() { return (_a != 0); }
 
+	/**
+	 * Set to null/zero
+	 */
+	inline void zero()
+		throw()
+	{
+		_a = 0;
+	}
+
 	/**
 	 * Check if this address is reserved
 	 *