Use for imports that are corresponding to Qt 5.9, as much as possible.

Recommended imports are

```
import QtQuick 2.9
import QtQuick.Controls 2.2
import QtQuick.Layouts 1.2
import org.kde.kirigami 2.5 as Kirigami
import "."
```

Some files import

```
import QtQuick.Dialogs 1.2
import QtQuick.Window 2.2
```

If needed, import corresponding to Qt 5.11

```
import QtQuick 2.11
import QtQuick.Controls 2.4
```

