Create unit test for the JSON schema validation

For the upcoming JSON schema validation I have created a new test case.
Currently, it just contains a test against an empty JSON object.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Add file for a paster validator command

For a manual check of the schema validity I am going to write a paster
command that performs the check on all available datasets and creates a
report.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Set metadata to enable paster command

The setup.py was not complete yet for the paster command to work. I have
added the necessary code. In the next step, the package list will be
retrieved through the API.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>