Add metadata original portal to link checker data

In order to avoid querying further CKAN data when generating the link
checker report the metadata original portal is added to the information
recorded when logging a link failure.

Signed-off-by: Konrad Reiche <konrad.reiche@fokus.fraunhofer.de>
Get rid of separate logging file

The separate logging file that has been used from the beginning of this
project did not provide any advantages and only introduced possible
problems due to missing write rights.

Also there are already many logging files and another one makes it even
more obscure where to find which information. The logging will be done
in the fetch consumer file.

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