JSONAlchemy: enhance default value search

* Additionally to setting the default value, the meta-metadata for the
  field is guessed from the field definitions following this rule
  order: `creator`, `derived`, `calculated`. If none of them is found
  every meta-metadad field is set to `UNKNOWN`.

* Convenience property `additional_info` added to SmartJson

Signed-off-by: Esteban J. G. Gabancho <egabancho@gmail.com>
Records: enhance the API to create empty records

* The default values for the `addittional_info` are set:
  `master_format='json'`, `namespace='recordext'` and
  `model='__default__'`

* Add `set_default_values` option when creating any JSON strucutre

Signed-off-by: Esteban J. G. Gabancho <egabancho@gmail.com>