Add regular expression to specify spatial-code

I have added a regular expression to specify the spatial-code field.

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

Just made a small change to the spatial-code description.

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