This module is an example of how to define, and implement a new plugin type in Drupal 8.

D8 documentation: https://www.drupal.org/developing/api/8/plugins

I've also written a couple of blog posts on the subject.

• http://drupalize.me/blog/201407/drupal-8-plugins
• http://drupalize.me/blog/201408/preparing-drupal-8-psr-4-autoloading
• https://drupalize.me/blog/201409/unravelling-drupal-8-plugin-system