Support Swedish Coordination numbers ("Samordningsnummer")

[sskogen]

No description provided.

[sskogen]

It could be possible to add this as a separate validator, and not as part of personnummer, but since the similar/corresponding D-number functionality in Norway is included in the norwegian fodselsnummer validator (and not as a separate validator), I found it more consistent to include Coordination numbers as part of the personnummer validator

[koblas]

Thanks for the change, looks good and I agree with your assessment about consistency.