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:         |                 Owner:  UnAssigned
  jinmei                             |                Status:  reviewing
                       Type:  task   |             Milestone:
                   Priority:  major  |  Sprint-20110816
                  Component:  data   |            Resolution:
  source                             |             Sensitive:  0
                   Keywords:         |           Sub-Project:  DNS
            Defect Severity:  N/A    |  Estimated Difficulty:  4.0
Feature Depending on Ticket:         |           Total Hours:  0
        Add Hours to Ticket:  0      |
                  Internal?:  0      |
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Changes (by vorner):

 * owner:  vorner => UnAssigned
 * status:  accepted => reviewing


Comment:

 Hello

 It should be ready for review. There's a merge with #1061 to bring in some
 trivial changes from there, which however cause a lot of changes and
 collisions. And it is based on yet unmerged branch, so the changes inside
 this branch can be requested by `git diff origin/trac1061...`.

 I implemented it not as a direct function on the DatabaseAbstraction
 (originally DatabaseConnection), as it seems to be wrong way to do so for
 some databases, like sqlite3, but as another object. The object can hold
 the whole connection if needed, or just the one statement in progress. I
 also included interation of in-memory data source.

 One possibly controversial thing is the use of NotImplemented as the
 default behaviour. I do it because some user might want to try writing his
 own data source sometime in future and this will help him try it quickly,
 without having to implement too many empty methods.

 With regards

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Ticket URL: <http://bind10.isc.org/ticket/1067#comment:4>
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