Add Encrypt support to the clients

This change adds Encrypt operation support to the KMIPProxy and
ProxyKmipClient clients, including unit tests to cover the new
functionality.

Extensive documentation has been added to the header comments for
the new client methods detailing the expected input parameters and
return values. This approach should be followed for all new client
additions going forward.

kmip/tests/unit/pie/test_api.py

@@ -59,6 +59,18 @@ class DummyKmipClient(api.KmipClient):
     def destroy(self, uid):
         super(DummyKmipClient, self).destroy(uid)
 
+    def encrypt(self,
+                data,
+                uid=None,
+                cryptographic_parameters=None,
+                iv_counter_nonce=None):
+        super(DummyKmipClient, self).encrypt(
+            data,
+            uid,
+            cryptographic_parameters,
+            iv_counter_nonce
+        )
+
     def mac(self, data, uid, algorithm):
         super(DummyKmipClient, self).mac(data, uid, algorithm)
 
@@ -147,6 +159,14 @@ class TestKmipClient(testtools.TestCase):
         dummy = DummyKmipClient()
         dummy.destroy('uid')
 
+    def test_encrypt(self):
+        """
+        Test that the encrypt method can be called without error.
+        :return:
+        """
+        dummy = DummyKmipClient()
+        dummy.encrypt('data', 'uid', 'crypto_params', 'iv')
+
     def test_mac(self):
         """
         Test that the mac method can be called without error.