Add server support for Getting wrapped keys

This change adds support for retrieving wrapped keys from the KMIP
server. The only supported key wrapping algorithm currently is
the AES-based NIST Key Wrap algorithm (RFC 3394). MAC/signing is
not supported for key wrapping. Attribute-bundling with the wrapped
key value is not supported. Wrapping of the entire key block TTLV
encoding is not supported. Various additional error cases are
included and checked for.

Unit tests covering the additions to Get are included.

kmip/core/exceptions.py

@@ -57,6 +57,28 @@ class CryptographicFailure(KmipError):
         )
 
 
+class EncodingOptionError(KmipError):
+    """
+    An encoding error generated during key wrapping.
+
+    This error is generated during key wrapping when a requested encoding
+    option is not supported or is incompatible with other settings in the
+    key wrapping request (e.g., attributes are requested with the key but
+    the encoding does not support wrapping attributes with the key value).
+    """
+    def __init__(self, message):
+        """
+        Create an EncodingOptionError.
+
+        Args:
+            message (string): A string containing information about the error.
+        """
+        super(EncodingOptionError, self).__init__(
+            reason=enums.ResultReason.ENCODING_OPTION_ERROR,
+            message=message
+        )
+
+
 class IllegalOperation(KmipError):
     """
     An error generated when an improper operation is attempted. The operation