is v4 support folder structure?

https://beta.ionicframework.com/docs/building/migration is written like structure.

```
src/
├── app/
　 ├── components/
　 ├── services/
　 └── pages/
```

But starter template and `ionic g` don't support this structure. I have not chased for a long time, what has become of this problem?

If Ionic team is waiting for implementation, I would like to challenge this. or If it keeps going, I would like to make option `ionic g -d`(`--directory`).

I believe that Ionic v3 structure supported many beginner's learning, this structure is great. so
I also want to make it standard specification in v4.

thanks.

先查看 https://beta.ionicframework.com/docs/building/migration 的遷移文件，並將其資料夾結構與目前的 starter template 以及 `ionic g` 的行為進行比較。判斷 v4 是否應支援該結構，或 `--directory` 選項是否才是預期結果；當專案方向和由此產生的 CLI 行為定義完成後，該 issue 即告完成。

由索引模型根據 Issue 內容生成。