[TIMOB-12567] BlackBerry : If 'top' & bottom' proporties are missing then the controls are not centered

Description: 1.Build & run KS on BB simulator or device 2.Goto controls -> slider -> change min/max OR 1.Run the code below on BB simulator/device

var win = Ti.UI.createWindow();
var slider = Ti.UI.createSlider({
	    value: 0,
	    min: 0,
	    max: 100,
	    left:10,
	    right:10
});
win.add(slider);
win.open();

Actual results: 1.We see the slider on the top rather than in the center Expected result: According to pedro the layout engine should center the controls when the top & bottom proporties are missing