Merge: add attribute annotation `noinit` to skip the attribute in inits

Merge: add attribute annotation `noinit` to skip the attribute in inits

~~~.rb
class Toto
   var tata: Int is noinit
   var tutu: String
end
var t = new Toto("hello") # only tutu in the constructor
~~~

Pull-Request: #600
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>