added BST() functionality
added private size() functionality
added the public size() functionality
added the public and private find() functionality
added keyExists() functionality
added max() and min() functionality
Added some not complete code to private add() and also added the framework for removeAllNodes()
changed removeAllNodes() to a return type of Node<Key, T>* from void. Also added removeAllNodes() functionality.
added ~BST() functionality
changed some stuff :3