Folding angular_dynamic.dart into angular.dart

Basically renamed angular.dart to angular_core.dart (unsure about naming here- sort of conflicts with the core lib) and renamed angular_dynamic.dart to angular.dart. Then exported angular_core.dart from angular.dart and angular_static.dart.

This addresses bug https://github.com/angular/angular.dart/issues/863 to allow a single 'angular.dart' import for the dynamic case which will be re-written from the transformer.