Relationships between Technology instances

Update SQL DB:
  ALTER TABLE `projects_technology` ADD `parent_technology_id` integer AFTER `name_url`;
  ALTER TABLE `projects_technology` ADD CONSTRAINT `parent_technology_id_refs_id_bbef66f5` FOREIGN KEY (`parent_technology_id`) REFERENCES `projects_technology` (`id`);

eg. Django => Python
eg. SDL => C/C++