BIND 10 #1062: add a base for DatabaseZoneHandle::find()

[BIND 10 Development]

#1062: add a base for DatabaseZoneHandle::find()
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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 is the first step to support normal query lookup in database
 backends.  This task includes:

 - define DatabaseConnection::searchForRecords() method.  It takes a
   zone ID and a domain name, and invokes a search for matching rows of
   that condition in the underlying database.  This method does not
   necessarily complete all transactions with the database.  The actual
   matching rows will be retrieved via the getNextRecord() method.
 - Define DatabaseConnection::getNextRecord() method.  It passes a
   reference to vector<string>, and let the underlying implementation
   fill in it with the columns of the next matching row as a result of
   searchForRecords().
 - implement SQLite3Connection versions of these methods.
 - implement a simplest form of DatabaseZoneHandle::find().  It only
   considers exact domain name matches (RR type, CNAME, NXRRSET) and
   NXDOMAIN (without wildcard consideration) case should be covered.

 For prototype implementation, see commit
 f57f8eef2d3d376ecedabc7fb7d3372784e2d429 of trac817a.
 (but the actual implementation doesn't have to stick to the way that
 the prototype does)

 This task depends on #1060 and #1061.

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Ticket URL: <http://bind10.isc.org/ticket/1062>
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BIND 10 Development