Add parsing of count meta-metadata field

Since I have added a count meta-metadata field to data dumps it is now
displayed properly, too.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add admin metadata controller and update routes

For the metadata creation I think its better to add them to the routes.
This way I can also use a separate controller class for the code. The
routes are now updated accordingly. Mainly I had to update the
constraints configuration.

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

Once more I add the metadata class that was also used in the harvester
before refactoring.

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

I have implemented the metadata importer. However, it is not worked
correctly yet. I cannot import the metadata without running into mapping
exceptions. This solution persists the record as a string which might be
an alternative approach.

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