Add support for non-binary sex identifiers ('3' and '9')

[cmrn]

SLK581 supports 4 possible codes in the sex field:

• 1: Male
• 2: Female
• 3: Intersex
• 9: Not stated / Not reported

(more info on the Aristotle Metadata Registry)

The decoder should be updated to support codes '3' and '9'. For these codes, both the male and female name lists should be used to decode the SLK.

The SLK creator should also be updated to allow users to generate SLKs with these codes.