Fixing some dart2js compilation issues for todo demo

One is that the publishAs parameter was removed from NgDirective constructor with (https://github.com/angular/angular.dart/commit/c48433e0350d4b374614eef8a0c9036805535dcb)

The other is a warning from the dart2js compiler that 'NodeTreeSanitizer' is not known- strings in @MirrorsUsed use the full lib name (but not for core types?)