Module import planner, and implement import declarations about pikelet HOT 2 CLOSED

let mut pikelet = Pikelet::new();

pikelet.load_module("test1", "
    let prelude = import prelude;
    in 
        record {
            foo = prelude.prim.u32.add 1 2;
            bar = prelude.id String "1";
        }
").unwrap();

pikelet.load_module("test2", "
    let prelude = import prelude;
        test1 = import test1; 
    in
        prelude.prim.u32.to-string test1.foo
").unwrap();