Allow map to have focus on startup

Currently unless you are using Google Chrome, you have to click on the map before it will respond to mouse events. For example if you start an ArcGIS Viewer for Flex app and roll the mouse wheel to zoom in or out the map it will not respond until the map has focus. With a small change to the index.mxml the map can be set to have focus on start up and it will instantly respond to mouse actions such as wheel zooming.