DQueue

Double ended queue Implements a nested class DoubleNode for building doubly-linked lists, where each node contains a reference to the item preceding it and the item following it in the list (null if there is no such item). Then implements methods for the following tasks: • Insert at the beginning • Insert at the end • Remove from the beginning • Remove from the end • Insert before a give node • Insert after a given node • Remove a given node • Move to front (move an object to the front) • Move to end (moved and object to the end)