Add list of Cordova plugins to `ionic info`

Cordova plugins or their versions often cause problems for building apps or running apps on specific devices (with specific Android versions). It would help a lot if `ionic info` would also output a list of the installed Cordova plugins and their versions.

Examples where this would help to solve things:
- cordova-plugin-ionic-webview on Android <5
- console plugin still installed with cordova-ios 4.5.x

從 `ionic info` 命令開始，追蹤它如何收集目前回報的資訊。確認如何納入已安裝的 Cordova 外掛程式及其版本，然後使用包含 issue 中所述範例外掛程式的專案驗證輸出。當 `ionic info` 清楚列出已安裝的外掛程式及其版本，足以協助排解建置和裝置問題時，即視為完成。

由索引模型根據 Issue 內容生成。