Extend scope of the module to all entites/bundle

The relevant_content module is currently limited to find relevant content on nodes, and that's a limitation inherited from Drupal 6. Given that Drupal 7 comes with entities and bundle, all bundles should be exposed. One use case I have is when building user profile (I''m using profile2 but using the regular user with a term reference field would be identical), you might want to find other users sharing some terms; typical use case is to find user with similar interests.