library
- also handle collapsed items in the changed notify event
- add new method which will collapse all items
- make sure our items have identifiers also when new lists are set
- improve notifyAdapterItemRangeChanged and also make sure items within the range are collapsed
- make sure all items are collapsed when a new list is set. to properly animate changes
sample
- add new ExpandableItem to showcase how to properly animate views inside items
- remove .debug from the package name
- improve AdvancedSampleActivity