Add circles on the map.

New Modules.Map.Circle object
Use the Modules.Map.createCircle method to create a route.
Properties :
- center: MapPointType, simple object representing a point on the map.
- radius: Float, the radius of the circle, specified in meters. It should be zero or greater.
- borderWidth: The width of the circle's outline, in Ti size (int, 'XXpx', 'XXdp'). The default value is 10px.
- borderColor: The color of the circle's outline. The default value is black.
- backgroundColor: The color of the circle fill. The default value is transparent.
- opacity: Float, the opacity of the circle. The default value is 1.
- zIndex: Int, the order in which this tile overlay is drawn with respect to other overlays. The default value is 0, like 'auto'.
- visible: Boolean, indicates if the circle is visible or invisible. The default value is true.

New MapView methods :
- mapView.addCircle(circle);
- mapView.removeCircle(circle);
- mapView.removeAllCircles();

Example :
var Map = require('ti.map');
var mapview = Map.createView({mapType:Map.NORMAL_TYPE});
var circle = Map.createCircle({
	center: {
		latitude:37.390749,
    	longitude:-122.081651
	},
	radius:650,
	borderWidth:'1dp',
    borderColor:'#D2BE1F',
	backgroundColor:'#FFE725',
    opacity:0.3
});

mapview.addCircle(circle);