chore: fixed all links to relative. also added linter for that

* also set up redirects

Author: Jelledb

.textlintrc

@@ -37,6 +37,7 @@
         "https://docs.cloudfoundry.org/concepts/roles.html",
         "https://docs.cloudfoundry.org/concepts/architecture/uaa.html#scopes"
       ]
-    }
+    },
+    "@elasticpath/no-dead-relative-link": true
   }
 }