hop_tasks: fixed Dart Analyzer task for windows
hop_tasks: fixed dart2js on windows
hop_tasks: unify code for windows-specific dart SDK exes
test: hop_tasks: moving exit code tests to dart scripts

hoping to make things a bit easier for cross-plat testing

...assumes 'dart' is in the path, though
v0.15.0.2
Merge branch '0-15-stable'
test: harness_browser: using unittest/test_controller.js

no points for coding it myself