[Nitro] properties

[TRANS]

In considering this more, I do think it a good idea to make the ORM as
transparent as reasonably possible. in which case, simply annotation
is the clearest case.

  class Foo
    attr :x
    ann :x, String, :default => "n/a"
  end

And if we want to take it further we can modify the built in attrbute
methods to accept annotations.

  class Foo
     attr :x, String, :default => "n/a"
  end

That just seems the Least Path of Resistance.

We still need a way to access the list of "properties"; shuoldn't we
think in terms of the database? Postgresql used to refer to them as
'attributes', but more commonly I think we refer to them as 'fields'
or better 'columns'.

T.