Pebble: remove notifications when dismissed on the phone (#326)

Most of the code is generic, so it could be implemented by other devices.
I dont know what happens if multiple messages arrive in the same notification.
So, this is experimental.

app/src/test/java/nodomain/freeyourgadget/gadgetbridge/service/TestDeviceSupport.java

@@ -54,6 +54,11 @@ class TestDeviceSupport extends AbstractDeviceSupport {
 
     }
 
+    @Override
+    public void onDeleteNotification(int id) {
+
+    }
+
     @Override
     public void onSetTime() {