Add clearLocalNotification method

[FlorianGerhardt]

As discussed in #371 there is no way to remove a notification from the notification centre.
This PR adds a method that removes a notification by id from the centre.

[TheBerg]

This is great, I was just looking into this.

We should probably also support removing via a tag too.

     * Cancel a previously shown notification.
     * @param tag the string identifier of the notification.
     * @param id the ID of the notification
     */
    public void cancel(@Nullable String tag, int id)

Let me know if you need help. :)

[rstiyer]

Could you please give an example of how to use this function?

I've tried calling PushNotification.clearLocalNotification(id) and PushNotification.clearLocalNotification({ id }) and neither works for me.

[joshbax]

This method only works on Android.
React-native is intended to be a cross platform framework. If you can't avoid adding platform specific functions, at the very least they should be documented or appropriately named (e.g. clearLocalNotificationAndroid())

[noway]

agree with @rstiyer how to use it?

[noway]

this is how:

PushNotification.clearLocalNotification(parseInt(notificationToRemove.androidNotificationId, 10));