Fix ISO8211 array description strings (subfield label separator '!' spuriously output before first subfield if field is repeating).
Fix S-57 data structure types for SG2D and SG3D according to S-57 maintenance document 8.
Remove duplicate unit and field terminators from S-57 output; they are added by the ISO8211 implementation.
Don't output SG2D field for S-57 edges consisting of a straight line between two connected nodes (as per section 5.1.4.4 in the S-57 specification).
Allow customization of S-57 metadata in the DSID, DSSI, and DSPM fields through layer creation options.