Add FullMangaSerializer, fixes manga library button bug

```
{manga: {...}, manga_library_entry: {...}, manga_library_entries: [...]}
```

The JSON returned from `MangaLibraryEntryController#create` would cause Ember to issue a GET request on `manga_library_entry/{id}`, which would 404 and cause an infinite loading state while it waited for data.

This PR matches the functionality of the anime page by adding a `FullMangaSerializer` so the returned data  is as expected.

```
{manga: {...}, manga_library_entry: {...}}
```

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I am unsure about the rename of `manga.js` to `00_manga.js`, this change was to make sure `Manga` was loaded before `FullManga` so that it could extend it.

Is there a better way to approach this? maybe require each model in the correct order rather than the tree?