Revise dump handler implementations and tests

I have learned that the value returned by the hash_start and array_start
callback methods is used for further references on the hash/array. This
means that I can drop the stack approach altogether.

This way the implementation is a lot easier. I have also revised the
next. Since this works very well now, the next step is to get the
callback handler working. Currently, it is only invoked once.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Complete dump handler implementation

It seems to me the dump handler is now completed and should work as
tested. Apparently, the problem with the callback has been solved by
clearing the working set array instead of assigning the null to the
reference.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Rewrite wrap methods to post-process record dumps

Now where the dump handler has been finished it was integrated into the
static dump download routines. The input stream for the dumps is opened
and passed to the Oj parse method with the dump handler instance.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>