Bugfix: registering localNotifications callbacks

The functions for registering callbacks on local notification interactions didn't work (as described in the docs). 

Changed the signature to allow passing in a callback:

```$cordovaLocalNotification.onClick(function (id, state, json) { console.log("pwnies!"); }); ```

Also changed capitalization of the functions for consistency. This works fine.

Note: I didn't update the docs and the onCancel callback doesn't seem to be called on cancel (Android), but that's probably some other bug.