Parse the specified XmlNode and decorate the supplied ObjectDefinitionHolder, returning the decorated definition.
The decorated definition (to be registered in the IApplicationContext/IObjectFactory), or simply the original object definition if no decoration is required. A null value is strickly speaking invalid, but will leniently treated like the case where the original object definition gets returned.
Implementations may choose to return a completely new definition, which will replace the original definition in the resulting IApplicationContext/IObjectFactory.
The supplied ParserContext can be used to register any additional objects needed to support the main definition.