Use new Cordova scheme

I had difficulty getting the app to build properly (issue #17) because there are no instructions on adding the Barcode Scanner plugin library. So I created a new Cordova project , moved the assets/www to cordova/www; AndroidManifest.xml, res/ across  to cordova/platforms/android/ and changed DroidGap to CordovaActivity in the java file and updated the README with instructions on how to add the Barcode Scanner plugin and build the app with the cordova.

I'm no programmer and only just got to grips with Cordova yesterday, but the apps seems to work OK for me this way.