Adding AttributeController tests
Fixing @return doc in FormHelper::renderForm()
Fixing AttribtueController and ProjectController actions so when the form content has to be returned as part of the JsonResponse, it correctly fetches the content
Removing "redirectUrl" in the JsonResponse for ProjectController:editAction as it is not relevant, fixing phpdoc
Removing unused "errors" key in the ProjectController::editAction response
Adding ProjectController tests
Fixing mock return values in AttributeControllerTest
Extracting some mock behaviours into train* methods to improve test readability