Adds to the functionality in Leaf Node by providing
a list of child nodes, in this case using the common and versatile Children.Keys
.
It adds support for adding new subnodes, handling pastes of various types of data and converting
them, and reordering child nodes.
The children class (separate) shows how you can lazily determine what the children should be (only when the parent is expanded), including garbage collecting them after a period of disuse; create nodes corresponding to various abstract keys which represent them; and manipulate the key set in various ways, usually in cooperation with the parent node. The icon set for the parent may provide a different appearance when the node is expanded.
The default executor lets you see a test sample of the node inside the IDE.