Update object hierarchy read/write to support the KMIP version

This change updates the PyKMIP object hierarchy's read/write
method signatures to support propagation of the KMIP version. The
introduction of KMIP 2.0 introduces future KMIP message encodings
that break backwards compatibility; to support this, PyKMIP must
know what KMIP version is being used when encoding or decoding an
object; the KMIP version residing in the client or server alone
is now insufficient. Prior versions of KMIP, namely 1.0 - 1.4,
have been backwards compatible, obviating the need for the KMIP
version at encode/decode time. Going forward, this is no longer
true.

The PyKMIP client and server have been updated to include the
KMIP version when making calls to read/write, as have the
associated test cases covering this functionality.

kmip/services/server/engine.py

@@ -116,6 +116,7 @@ class KmipEngine(object):
             contents.ProtocolVersion(1, 0)
         ]
 
+        self.default_protocol_version = self._protocol_versions[2]
         self._protocol_version = self._protocol_versions[2]
 
         self._object_map = {
@@ -308,7 +309,7 @@ class KmipEngine(object):
             response_batch
         )
 
-        return response, max_response_size
+        return response, max_response_size, header.protocol_version
 
     def _build_response(self, version, batch_items):
         header = messages.ResponseHeader(