QML imports are currently not all consistent.
We should use this example as a base (versions can of course be different, only use needed imports) and apply it everywhere:
```
import QtQuick 2.5
import QtQuick.Layouts 1.0
import QtQuick.Controls 2.5 as QQC2
import QtQuick.Dialogs 1.1 as QtDialogs
import org.kde.kirigami 2.5 as Kirigami
import org.kde.plasma.core 2.0 as PlasmaCore
import org.kde.plasma.components 2.0 as PlasmaComponents2
import org.kde.plasma.extras 2.0 as PlasmaExtras
```