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`` to link to fields and
  propagate changes from one to the other 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@cern.ch>