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 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 checker module.

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