added relationships in the entity view

Added a default relationships view in the GET for entities.

e.g.

{
  "todos": [
    {
      "doneStatus": "FALSE",
      "guid": "fc2c7068-102e-4602-a9f7-1e5c9c869306",
      "description": "",
      "title": "file paperwork",
      "relationships": [
        {
          "task-of": [
            {
              "projects": [
                {
                  "guid": "cbb77a23-6e96-4747-8b07-6223f078b428"
                }
              ]
            }
          ]
        }
      ]
    },
   ...

NOTE: cannot amend relationships using POST or PATCH on Entities yet, and can not configure this view.