include some project data in challenge queries (#1260)

* include some project data in challenge queries

* Revert embedded project object from project listChildren

insertProjectJSON replaces a challenge's numeric `parent` with the full
project object, which breaks the maproulette-java-client integration
tests: ProjectAPI.children deserializes Challenge.parent as a long.
GET /project/:id/challenges keeps the scalar parent; exploreChallenges
still embeds the project.

Author: CollinBeczak

app/org/maproulette/controllers/api/ChallengeController.scala

@@ -1171,7 +1171,7 @@ class ChallengeController @Inject() (
           difficulty = difficulty
         )
 
-        Ok(Json.toJson(challenges))
+        Ok(insertProjectJSON(challenges))
       }
     }