Add Get-EditorCommand and $psEditor.GetEditorCommand()

The way it is currently setup, it can be very difficult to determine what the Editor Command Names are that are loaded. The user is only shown the Display Name, so they will actually have to go look at the source code of the Register-EditorCommand to get the name.

This makes it difficult to unregister Editor Commands if you do not already know exactly what the command's name is. This will become more problematic once people start integrating their commands into modules.

まず、既存の Register-EditorCommand のフローと、読み込まれたエディター コマンドが現在どのように表示されているかを追跡します。ユーザーが Get-EditorCommand と $psEditor.GetEditorCommand() を通じてエディター コマンド名を確認でき、それらの名前を登録解除に利用できるようになった時点で、変更は完了です。