Use new loose JSON serialization in the JSONServiceAction. This makes *JSONSerializers obsolete.
Add JSON annotation for specifying json serialization hints
The only difference in serialization is the AssetEntryDisplay, field: getCategoryIds (in JSONServiceAction)
Previously, this field is serialized to 'assertCategoryIds' with CSV value.
Now this field is serialized to 'categoryIds' and the value is json array.