Removed < <= > >= from the API. Implemented as comparisons of the

underlying dictionaries, there were no reasonable use cases (lexicographic
sorting of a list of sets is somewhat esoteric).  Frees the operators
for other uses (such as strict subset and superset comparisons).

Updated documentation and test suite accordingly.

Lib/test/test_sets.py

@@ -419,12 +419,12 @@ class TestOnlySetsInBinaryOps(unittest.TestCase):
 
     def test_cmp(self):
         try:
-            self.other < self.set
+            self.other == self.set
             assert 0, "Comparison with non-set on left"
         except TypeError:
             pass
         try:
-            self.set >= self.other
+            self.set != self.other
             assert 0, "Comparison with non-set on right"
         except TypeError:
             pass