jsonalchemy: update `parser.py` for pyparsing 2

* Transform hardcoded decorators into extensions inside the parser
  folder. The new decorators are cataloged as before, on and after
  depending on when they should be evaluated.

* All the decorators that before needed always a tuple now works as
  `@decorator(*args)`.

* Remove `@inherit_from` decorator from field definitions as it is
  replaced by `@extend` and `@override`.

* New decorator extension added `@connect(field_name[, function])` to
  link to fields and propagate changes from one to the and vice versa.

* Remove `include` form field definitions as now registries are used.

* Replace `checker` section by `schema` to perform simple
  validations, like type or length. For more complex check use the
  checher module.

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
sqlalchemy: change JSON type to native one.

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
jsonalchemy: better definition of common fields

Signed-off-by: Esteban J. G. Gabancho <esteban.gabancho@gmail.com>
WIP