Allow an official way to achieve a "flat" ItemSelector appearance

[Michael Terry]

Design gave me some visuals for the welcome wizard. One of them (attached) shows a very "flat" looking ItemSelector.

I have three options in implementing that visual:

1) I can manually create that widget using pieces glued together. This guarantees it looks exactly right, but is harder to maintain.

2) I can get pretty close using an ItemSelector with OptionSelectorDelegates. This has some deltas from the desired look, which may be interesting to you folks, as examples of things a developer would want to do, but can't [1].

3) Wait for the SDK folks to provide a widget that can look like that.

I've implemented #2 in the short term, and will implement #1 in the medium term. But this bug is for the long term solution of #3.

[1] The things I wanted to do with #2 but couldn't (see attached number2.png screenshot):
- I couldn't remove the border
- I couldn't control fontSize (had to trick it by setting subText and leaving a blank text to get slightly smaller font)
- I couldn't control tick or divider color
(Maybe you *shouldn't* give me all that power as a developer. Just listing things that I would have needed to do to match the spec)

[Tim Peeters (tpeeters)]

ItemSelector does not have a border (only OptionSelector has), so what you are asking for is already there.

See http://developer.ubuntu.com/api/qml/sdk-14.10/Ubuntu.Components.ListItems.ItemSelector/

[Giorgio Venturi (giorgio-venturi-deactivatedaccount)]

Going forward, option selector is going to be deprecated in favour of ListItem selector.