add Tumbler to Qt QuickControls

Nokia gave Qt/QML the Tumbler object, part of the original Qt Quick Components for Symbian and Meego, cf. http://doc.qt.digia.com/qtquick-components-symbian-1.1/qml-tumbler.html

It was a neat way of enabling a user to pick an item from a list, by spinning through the list. Works great on a touch interface.

Some of the Qt Quick Components have now made their way into Qt5 (Qt Quick Controls). But the Tumbler is not among them. SpinBox and Slider are similar, but not the same.

I'd like to request to have the Tumbler added to Qt Quick Controls.

The old symbian/meego qml source code is still available (e.g. within https://qt.gitorious.org/qt-components/qt-components), but it’s not so trivial to port it across to Qt5.

That is to say, it's easy to make a trivial port, but the behaviour is inconsistent. For instance within the use I'm trying to create, some TumblerColumns appear more or less normally, the contents of others do not appear unless an inordinate width is used (e.g. width: 33 just to display a colon (, when width: 5 should do), others TumblerColumns do not display content at all. Not so trivial to sort it all out consistently.