Cleans up and removes TODOs, adds tests (#844)

* removes version ordering from v2; simplifies now-unecessary three-level faceting

* resolved some todos

* test for game version updating

* merge fixes; display_categories fix

src/routes/v3/version_creation.rs

@@ -583,8 +583,6 @@ async fn upload_file_to_version_inner(
     };
 
     let all_loaders = models::loader_fields::Loader::list(&mut **transaction, &redis).await?;
-
-    // TODO: this coded is reused a lot, it should be refactored into a function
     let selected_loaders = version
         .loaders
         .iter()