Merge: Generalized class members

This PR change the way class members are parsed.

Before, the order was strict: class annotations, then extern code block, then super clauses, then properties.
After, annotations and super clauses can appear in any order within the properties

The need is to enable class annotations inside the class (cf #1158) I did not find another simple way to do this.

Now, one can write
~~~nit
class B
   super A
   serializable
   var i: Int
   autoinit x, i
end
~~~

Pull-Request: #1159
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>

diff --cc src/modelize/modelize_property.nit
Simple merge

diff --cc src/parser/parser_nodes.nit
Simple merge

diff --cc tests/sav/test_parser_args1.res
Simple merge