Translate QML-only messages with QTranslator

[notmart]

Some messages are needed to be in the QML file directly, this means they can't be translated from the python part, so use the internal Qt translation infrastructure.
see https://doc.qt.io/qt-5/qtquick-internationalization.html

All qml files will need to do text messages with the qsTr method call like so:

Label {
    text: qsTr("Text to be translated")
}