serialize attributes with maxOccurs >1 to list in RDB

[pahjbo]

In the special case where an attribute has maxOccurs > 1 and has a type that is a PrimitiveType the attribute can be serialised to a comma separated string in a column of the RDB

It should be noted that the current behaviour in the generated Java code is to use a list and a join table - but this clearly is more complex than the suggested solution and requires more complex querying.

[glemson]

Could this be a JSON array? That might also be an approach for mapping attributes with structured data types, iso mapping them to multiple columns as one would do in standard ORM. I'll write an issue for that.