Consolidate and re-organize testcases

testcases/Account.scala

testcases/AddressBook.scala

testcases/Interpret.scala

testcases/MutuallyRecursive.scala

testcases/Naturals.scala

testcases/PropositionalLogic.scala

testcases/README

testcases/SimpInterpret.scala

testcases/datastructures/AmortizedQueue.scala

testcases/datastructures/BinarySearchTree.scala

testcases/datastructures/BinaryTrie.scala

testcases/datastructures/HeapSort.scala

testcases/datastructures/InsertionSort.scala

testcases/datastructures/LeftistHeap.scala

testcases/datastructures/ListWithSize.scala

testcases/datastructures/MergeSort.scala

testcases/datastructures/QuickSort.scala

testcases/datastructures/RedBlackTree.scala

testcases/datastructures/SortedList.scala

testcases/datastructures/TreeListSetNoDup.scala