Fix in DecimalTagMapper, adding the missing line.
Enable nesting in *TaggedPackager other composite fields

Introduction ISOSubPackager allows obtaining field number required
for nesting other complex fields (e.g. GenericSubFieldPackager
or even GenericTaggedPackager) in TaggedPackager's
Merge pull request #57 from demsey/taggedpack

Enable nesting in *TaggedPackager other composite fields