Add support for the Sensitive attribute

This change adds support for the Sensitive attribute, adding it to
the attribute factory, the SQLAlchemy object hierarchy, and to the
server attribute handling methods. The intent is to use this new
attribute to test the new SetAttribute and ModifyAttribute
operations coming in future commits. Unit tests have been added
and modified to support the new additions.

kmip/tests/unit/services/server/test_engine.py

@@ -1757,6 +1757,10 @@ class TestKmipEngine(testtools.TestCase):
                 enums.CryptographicUsageMask.DECRYPT
             ]
         )
+        sensitive = attribute_factory.create_attribute(
+            enums.AttributeType.SENSITIVE,
+            True
+        )
         managed_object = pie_objects.SymmetricKey(
             enums.CryptographicAlgorithm.AES,
             0,
@@ -1771,6 +1775,7 @@ class TestKmipEngine(testtools.TestCase):
         )
         self.assertEqual(0, managed_object.cryptographic_length)
         self.assertEqual([], managed_object.cryptographic_usage_masks)
+        self.assertFalse(managed_object.sensitive)
 
         e._set_attribute_on_managed_object(
             managed_object,
@@ -1809,6 +1814,13 @@ class TestKmipEngine(testtools.TestCase):
             managed_object.cryptographic_usage_masks
         )
 
+        e._set_attribute_on_managed_object(
+            managed_object,
+            ("Sensitive", sensitive.attribute_value)
+        )
+
+        self.assertTrue(managed_object.sensitive)
+
     def test_set_attribute_on_managed_object_unsupported_features(self):
         """
         Test that the right errors are generated when unsupported features