Is the custom/modules/relationship directory still needed? Some of the functionality seems to be moved elsewhere.

I am on SugarCRM 8.0.2.  When I worked with relationships in the past, I noticed that a file was created and put in ./custom/Extension/modules/relationships/relationships, but it was not used, instead ./custom/metadata/{relationshipName}MetaData.php was. 

Are all the files in the relationship directory no longer useful. If some still are useful, which ones?