Rewrite the JSON recursive parse method

The JSON recursive parse method was too general. I went back to a more
simple implementation which is tailored for the CKAN case. It must not
normalize String encoded numbers of boolean values.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Create CKAN specific class for the JSON recursion

The recursive parsing should really not be a general method to work on
everything. It is really just needed for the CKAN extras fields. Hence,
I have changed the whole namespace.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Apply normalize extras to dump download, too

The normalization of extras was not applied to dumps until now. This way
data.gov.uk and govdata.de are normalized as well.

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