get sdk libraries working

[jmesserly]

SDK libraries (dart:*) are not remotely close to working in JS. This is a tracking bug.

[jmesserly]

the primitive types might be a good place to start: Object, bool, int, double, String. And List, Map (those a a little different, as they probably kind of work already). See also #40.

Currently Object is generating non-sensical class Object extends dart.Object :)

[jmesserly]

CC @vsmenon

[jmesserly]

baby step: https://codereview.chromium.org/1020043002/

[jmesserly]

there's probably still issues (e.g. mirrors), but we can track them on their own. It should mostly work now.