Adding the ManagedObject base class

This change adds ManagedObject, the abstract base class of the
simplified KMIP object hierarchy. It defines a set of attributes common
to all KMIP objects and registers placeholder methods to be implemented
by all subclasses. A basic test suite is included, using a dummy
ManagedObject subclass for testing.

kmip/pie/objects.py

@@ -0,0 +1,100 @@
+# Copyright (c) 2015 The Johns Hopkins University/Applied Physics Laboratory
+# All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+from abc import ABCMeta
+from abc import abstractmethod
+
+from six import add_metaclass
+
+
+@add_metaclass(ABCMeta)
+class ManagedObject:
+    """
+    The abstract base object of the simplified KMIP object hierarchy.
+
+    A ManagedObject is a core KMIP object that is the subject of key
+    management operations. It contains various attributes that are common to
+    all types of ManagedObjects, including keys, certificates, and various
+    types of secret or sensitive data.
+
+    For more information, see Section 2.2 of the KMIP 1.1 specification.
+
+    Attributes:
+        value: The value of the ManagedObject. Type varies, usually bytes.
+        unique_identifier: The string ID of the ManagedObject.
+        names: A list of names associated with the ManagedObject.
+        object_type: An enumeration associated with the type of ManagedObject.
+    """
+
+    @abstractmethod
+    def __init__(self):
+        """
+        Create a ManagedObject.
+        """
+        self.value = None
+
+        self.unique_identifier = None
+        self.names = list()
+        self._object_type = None
+
+        # All remaining attributes are not considered part of the public API
+        # and are subject to change.
+        self._application_specific_informations = list()
+        self._contact_information = None
+        self._object_groups = list()
+        self._operation_policy_name = None
+
+        # The following attributes are placeholders for attributes that are
+        # unsupported by kmip.core
+        self._archive_date = None
+        self._initial_date = None
+        self._last_change_date = None
+
+    @property
+    def object_type(self):
+        """
+        Accessor and property definition for the object type attribute.
+
+        Returns:
+            ObjectType: An ObjectType enumeration that corresponds to the
+                class of the object.
+        """
+        return self._object_type
+
+    @object_type.setter
+    def object_type(self, value):
+        """
+        Set blocker for the object type attribute.
+
+        Raises:
+            AttributeError: Always raised to block setting of attribute.
+        """
+        raise AttributeError("object type cannot be set")
+
+    @abstractmethod
+    def __repr__(self):
+        pass
+
+    @abstractmethod
+    def __str__(self):
+        pass
+
+    @abstractmethod
+    def __eq__(self, other):
+        pass
+
+    @abstractmethod
+    def __ne__(self, other):
+        pass