[TIMOB-10235] iOS: Make navigation controller optional in tabs

Feature request

Make the navigation controller of the tab optional. A native tab controller does not come with the navigation controller built in. We ship with it because it makes sense and it is very useful. There are occasions, tho, that the developer needs to have a window without the navigation part. For example, placing a tab group inside a split window, or vice versa. The developer can remove the tab bar by hiding it, but the navigation controller will still be there creating overhead.

Backwards compatibility

Of course, we don't want to break all the apps out there using the stands tab group component. So this should be an optional boolean in the creation of the tabs it self.

Proposed example

var tabGroup = Ti.UI.createTabGroup();
var win = Ti.UI.createWindow({
    backgroundColor: 'white'
});
var tab1 = Ti.UI.createTab({
    window: win,
    navigation: false
});
tabGroup.addTab(tab1);
tabGroup.open();