Adding operation policy name support to the client

This change adds operation policy name support to the pie client,
allowing you to optionally specify the policy name when creating
new symmetric keys and asymmetric key pairs. The operation policy
name can also be set on any pie object and will be sent with the
corresponding register request for new objects. Tests for these
additions are included.

kmip/pie/objects.py

@@ -52,6 +52,11 @@ class ManagedObject(sql.Base):
     _names = relationship('ManagedObjectName', back_populates='mo',
                           cascade='all, delete-orphan')
     names = association_proxy('_names', 'name')
+    operation_policy_name = Column(
+        'operation_policy_name',
+        String(50),
+        default='default'
+    )
 
     __mapper_args__ = {
         'polymorphic_identity': 'ManagedObject',
@@ -71,6 +76,7 @@ class ManagedObject(sql.Base):
         self.unique_identifier = None
         self.name_index = 0
         self.names = list()
+        self.operation_policy_name = None
         self._object_type = None
 
         # All remaining attributes are not considered part of the public API
@@ -78,7 +84,6 @@ class ManagedObject(sql.Base):
         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