also added some more hack to the DB unittests so add/delete zone tests
can work with mock accessor, too.

And a minor cleanup in the code

don't duplicate the duplicate zone check in sqlite3 accessor's addZone()
added documentation

Note: currently called createZone so as not to interfere with an existing addZone() call in MemoryClient.
Instead of pure virtual I made it have a default 'NotImplemented' method.
Also, the DatabaseClient holds the transaction (not the SQLite3Accessor); we could do it on that level but we already have a transaction API on a higher level and it makes a little bit more sense to me to do it there

See bug #2367 for the fix-scaffolding.py tool.

- RAII InMemoryClient's createInstance
- remove dead code
- added more comments

Made the getZoneCount() method from inmemory client a general datasource client
call (which throws NotImplemented by default), as this does seem useful in other
 cases as well.

Now the work starts to pay off; removed the temporary pointer variable (getInMemoryClientP() still returns a pointer but now directly retrieved from the container), and any direct reference to isc::datasrc::InMemoryClient is removed from au
th_srv (but not from tests as of yet)

change the return value of the journal reader factory to a pair of result
code and an object pointer.  added some more tests.

almost empty with bootstrap tests.

As the application can't call the constructor directly, it will be
passed from here.

Defaults to false as a backward compatibility (might be temporary)

with a slightly different interpretation; if false, treat differing TTLs as an indicator of different RRsets

and implement it for the sqlite3 backend
for the memory backend, it may not be necessary, but it might depend on how we add them

startUpdateZone() to be more consistent with getIterator()).

- defined updater and related classes
- implemented a simple constructor and updater finder

The default throws isc::NotImplemented to allow data sources not
supporting this feature.

It will look something like this, hopefully. Let's see if it works.

* Inherit the MemoryDataSrc from DataSourceClient
* Small comment cleanup
* Makefile fix
* Remove extra parts of MemoryDataSrc
  - FindResult is inherited from MemoryDataSrc and it was the same
    anyway, just different name.
  - Remove the private assignment operator and copy constructor, the
    DataSourceClient is already uncopyable.