BIND 10 #1067: support zone iterator in the new data source API

[BIND 10 Development]

#1067: support zone iterator in the new data source API
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            Reporter:  jinmei        |                        Owner:
                Type:  task          |                       Status:  new
            Priority:  major         |                    Milestone:  Next-
           Component:  data source   |  Sprint-Proposed
           Sensitive:  0             |                     Keywords:
         Sub-Project:  DNS           |              Defect Severity:  N/A
Estimated Difficulty:  0             |  Feature Depending on Ticket:
         Total Hours:  0             |          Add Hours to Ticket:  0
                                     |                    Internal?:  0
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 This task includes:

 - define the (abstract) ZoneIterator class
 - implement DatabaseZoneIterator class.
 - define DatabaseConnection::traverseZone() class.
 - implement SQLite3 version of traverseZone.

 See commit 144caea728054ddcd91c908c6177e089e20aa5ef of trac817a for
 prototype implementation.

 (but the actual implementation doesn't have to stick to the way that
 the prototype does)

 This task depends on #1060 and #1061, but otherwise can be done in
 parallel with other data source refactoring tasks.

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Ticket URL: <http://bind10.isc.org/ticket/1067>
BIND 10 Development <http://bind10.isc.org>
BIND 10 Development