Abstract static methods

Hi, trying to produce some generic code, I discovered that interfaces can't have non-implemented static methods.

But it would be a nice feature to allow this.

I can illustrate it by this piece of Rust code:

``` rust
struct A {
damn: i32
}

trait Serializable {
fn from_integer(nb: i32) -> Self;
}

impl Serializable for A {
fn from_integer(nb: i32) -> Self {
A {
damn: nb
}
}
}

fn bar(nb: i32) -> T {
T::from_integer(nb)
}

pub fn main() {
let wow = bar::(10);
println!("{}", wow.damn);
}
```

T bar(int nb) {
return T.fromInteger(nb);
}

main() {
var wow = bar(42);

print(wow.foo);
}

```