Updated the mechanism for native callbacks to Javascript side to conform to current Cordova documentation.

1. APPLocalNotification.m: updated the callback mechanism to conform to the current Cordova documentation, by replacing "self writeJavascript" with sendPluginResult, as documented at http://cordova.apache.org/docs/en/3.3.0/guide_platforms_ios_plugin.md.html#iOS%20Plugins.

2. Changed the arguments to local-notification.js/addNotification to get rid of the foreground and background function call names, and instead take a callback function which receives as its argument the following object:
{ 	ground: <'foreground' || 'background'>
	id: <the id you gave to addNotification>
}
Also modified local-notification.js to give a unique default id (system timestamp in hex format), and changed the default callback function to conform to the new arguments.