If specified will reuse existing items if a new item is created that has the same id.

The IdentityKey is a key into the provided objects. If the key is not found the item will not have an id, and will not be matched.

Matched items keep the same Node instances that they had before. This makes it suitable for using in combination with LayoutAnimation. It also makes it possible to use AddingAnimation and RemovingAnimation with Each, as the Node lifetime will now follow the logical lifetime.

This feature works in conjunction with replaceAt and replaceAll on Observable's.

NOTE: This feature, if using animations, does not yet operate well in combination with Reuse. It may result in reuse of unintended items and/or unexpected animations. https://github.com/fuse-open/fuselibs/issues/175