Static fields describing fields in DTO (FIELD_*) should be in validators
The 'FIELD_*' fields are only used in validators, so they should not be part of the DTO. One validator is generated for one DTO, and by default the "FIELD_ *" fields should only be used in it. However, for more flexibility in the way validators are written, these fields should be public.
This change will also prevent 'FIELD_*' fields from being generated for DTOs without validators (output messages).