Implement "state" function for remote

[evgenyigumnov]

Usage:

client_actor.state(|mut state| {
          // change state

        state
});

1. client_actor.state() >>> network >>> server_actor.state() >>> state.lock()
2. server_actor >>> network [state] >>> client_actor >>> |mut state| { ... }
3. client_actor >>> network [state] >>> server_actor >>> state.unlock()

Proof of concept code:

#[derive(Debug)]
struct A {
    a: i32,
}
fn main() {

    func(|mut c| {
        c.a = 2;
        println!("Hello, world! {:?}", c);
        c
    });
}

fn func<F>(f: F) where F: Fn(A) -> A {
    let mut z = A { a: 1 };
    z = f(z);
    println!("Hello, world! {:?}", z)
}