Upgrade for Dart 2.0

[eee-c]

Need to remove browser dependency. Switch back to inline ACE (ace package is not supported). Update SDK dependency. Fix code.

[uojiaku]

I'm getting "Dart 2 has a new build system. Learn how to migrate from pub build and
pub serve: https://dart.dev/web/dart-2" after doing "pub serve". I upgraded to Dart 2.8.1, commented out the browser, ctrl_alt_foo, ace and dependencies for me to successfully run "pub install" but how should I resolve this?