get rid of IntegerList interface and ... Output->
... update IntegerTreeNode.java to be identical to that used in exercises
    2 and 3 (pity I switched to using directories to order things
    a mistake in this case!).

-> Output of test remains unaltered:

	$ java TestIntegerTreeNode

	Create a tree like in exercise sheet Figure 1 with 6, 9, 5, 3, 11, 12, 8
	Note toString now simplified
	Point (a) have started with 6 as head. toString gives: [6]
	   The tree contains 1 values. It has a depth of 0
	Point (b) after 6, 9. toString gives: [6 [9]]
	   The tree contains 2 values. It has a depth of 1
	Point (c) after 6, 9, 5, 3 toString gives: [6 [5 [3]] [9]]
	   The tree contains 4 values. It has a depth of 2
	Point (d) after 6, 9, 5, 3, 11, 12, 8 toString gives: [6 [5 [3]] [9 [8] [11 [12]]]]
	   The tree contains 7 values. It has a depth of 3
	check whether tree contains 11 (it does) gives: true
	check whether tree contains 10 (it does not) gives: false
	The maximum value in the tree is 12, getMax gives: 12
	The maximum value in the tree is 3, getMin gives: 3
start working on 1.4 deletion of tree elements