optional<T> is now parsable, even if T is a class type.

Author: 5cript

parse/jsd_optional.h

@@ -10,12 +10,13 @@ namespace JSON
                PropertyTree const& object, ParsingOptions const& options = DEFAULT_PARSER_OPTIONS)
     {
         try
-        {
-            auto opt = object.tree.get_optional <T> (name);
-            if (!opt)
-                return; // its ok, it was optional
-            else
-                value = opt.get();
+        {
+            if (object.tree.get_optional <std::string> (name))
+            {
+                T v;
+                parse(v, name, object, options);
+                value = v;
+            }
         }
         catch (boost::property_tree::ptree_bad_data& exc)
         {