Remove serial

Adjust to the recent dart:js changes. jsify is now a ctor, and Serializable goes away.

I'm not totally happy about the loss of Serializable. This means that many of our pass-by-reference calls get converted to pass-by-value. So, created a set of args into a methods in the wrong order will lead to unexpected results. 

    foo.a = aRef;
    aRef.field = 'sdfsdf';
    files.openEntry(foo); // may not receive the field modification, depending on the type of field foo.a