Fix generic WsdlClass::__set_state() method in order to instantiate dynamically the object without any parameters.
Improve "from schema" meta storage by providing the constant WsdlToPhpModel::META_FROM_SCHEMA and two methods WsdlToPhpModel::setFromSchema() and WsdlToPhpModel::getFromSchema(). These two methods are then used within WsdlToPhpGenerator methods to store this information.
