Enable processing legacy validator code

Create a LegacyValidatorMapper to replace legacy validator configuration with the new valid configuration.

1. a 'resource-required' validator must be mapped to a 'required' validator
2. a 'non-empty' validator without a 'required' or 'optional' validator on an Html field must be mapped to a 'non-empty-html'  validator.
3. from a 'non-empty' and 'required' combination the 'non-empty' one is removed.