Fix for issue 2446 part #1.

Add support to the admin framework for specifying one or more "default" managed objects which should be created automatically when a parent managed object is created. The XML mark-up is provided as part of the parent managed object's relation definition as follows (the sample is taken from the LocalDBBackend XML definition):

     <adm:relation name="local-db-index">
       <adm:one-to-many naming-property="attribute">

         <adm:default-managed-object name="aci">
           <adm:property name="index-type">
             <adm:value>presence</adm:value>
           </adm:property>
           <adm:property name="attribute">
             <adm:value>aci</adm:value>
           </adm:property>
         </adm:default-managed-object>

         <adm:default-managed-object name="entryUUID">
           <adm:property name="index-type">
             <adm:value>equality</adm:value>
           </adm:property>
           <adm:property name="attribute">
             <adm:value>entryUUID</adm:value>
           </adm:property>
         </adm:default-managed-object>

         <adm:default-managed-object name="objectClass">
           <adm:property name="index-type">
             <adm:value>equality</adm:value>
           </adm:property>
           <adm:property name="attribute">
             <adm:value>objectClass</adm:value>
           </adm:property>
         </adm:default-managed-object>
       </adm:one-to-many>

The functionality is implemented on the client-side API in a generic manner so that it is independent of the underlying driver implementation (so the default indexes would be created if we had an offline direct to file driver as well).