Improvements to text layouting in QML

Description

Allow more control over the text layouting process in QML.

Give access to every text line through a hook, this gives the opportunity to position and resize a line as it is being laid out.
It is then possible to lay out the text in columns or around other objects.

line.number (read-only)
line.x
line.y
line.width
line.height

The behaviour of the text element (wrapping, sizing) should be preserved if possible.

Example code

Text {
    id: layout
    text: "..."
    width: 200
    onLineLaidOut: {
        if (line.number < 5) {
            line.x = 100
            line.width = line.width - 100
        }
    }
}

Make sure onLineLaidOut is not emitted if not connected.