Add tasks for all the new languages

Task/Tree-traversal/FunL/tree-traversal.funl

@@ -0,0 +1,36 @@
+data Tree = Empty | Node( value, left, right )
+
+def
+  preorder( Empty )          =  []
+  preorder( Node(v, l, r) )  =  [v] + preorder( l ) + preorder( r )
+
+  inorder( Empty )           =  []
+  inorder( Node(v, l, r) )   =  inorder( l ) + [v] + inorder( r )
+
+  postorder( Empty )         =  []
+  postorder( Node(v, l, r) ) =  postorder( l ) + postorder( r ) + [v]
+
+  levelorder( x ) =
+    def
+      order( [] )                 =  []
+      order( Empty         : xs ) =  order( xs )
+      order( Node(v, l, r) : xs ) =  v : order( xs + [l, r] )
+
+    order( [x] )
+
+tree =    Node( 1,
+            Node( 2,
+              Node( 4,
+                Node( 7, Empty, Empty ),
+                Empty ),
+              Node( 5, Empty, Empty ) ),
+            Node( 3,
+              Node( 6,
+                Node( 8, Empty, Empty ),
+                Node( 9, Empty, Empty ) ),
+              Empty ) )
+
+println( preorder(tree) )
+println( inorder(tree) )
+println( postorder(tree) )
+println( levelorder(tree) )