Add some fixes to the knowledge data

The URL for the Russian Police data portal was not complete. Also
removed another German word from the misspelling dictionaries. It
cannot be detected reliably.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add a maybe statement to the license substitution

The license identifier might be null, hence I have added a maybe
statement.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Use latest snapshot if snapshot cannot be found

A snapshot might be selected through the URL that is not available.
Instead of failing all together, the latest snapshot of the repository
is selected. What is still missing is an automated redirection.

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