QML Coordinate should be a value type, not passed by reference

QML Coordinate currently is an object that is passed around as a pointer (reference) in QML, when users will expect it to be a value type as it is in C++. See, for example, the issue with circle centers in mapviewer, where to obtain the expected semantics we had to change:

circle.center = point

to

var c = Qt.createComponent("import QtLocation 5.0; Coordinate { } ");
c.latitude = point.latitude;
c.longitude = point.longitude;
circle.center = c;

This is a fairly major API issue, as it violates the user's natural expectations about the semantics of passing around a Coordinate, which looks essentially like plain old data, but is not even close to it in behaviour.