JSON normalizers returns object instead of associative arrays

[jkowalleck]

Json normalizers returns object of stdClass instead of associative arrays

• therefore revisit the serializes in general and simplify them !

benefit:

• distinguish key-value stores from lists: lists/sets are arrays, key/value-stores are objects
• this will help typing a lot !

[jkowalleck]

gave it a try, did not like the outcome and the effort.
maybe this will be a feature for a later version.