Add larger Wear specific action icons.

The default notification action icon size is 48dp (32dp optical). However, those icons appear blurry on Android Wear devices as they expect 64dp (48 optical) sized action icons. By using WearableExtender, we specify the larger Wear icons for those actions. Note: we cannot use the same icon for both as the notification tray does NOT scale down the icons to 48dp so they appear much too large.