Adding support for the DiscoverVersions operation

This change adds support for the DiscoverVersions operation, including
updates to the KMIP client, the client and KMIP core test suites, and a
DiscoverVersions unit demo.

kmip/demos/utils.py

@@ -119,6 +119,8 @@ def build_cli_parser(operation):
             default=None,
             dest="length",
             help="Key length in bits (e.g., 128, 256)")
+    elif operation is Operation.DISCOVER_VERSIONS:
+        pass
     else:
         raise ValueError("unrecognized operation: {0}".format(operation))