refactor(core): change module semantics

This contains major changes to the compiler, bootstrap of the platforms
and test environment initialization.

Main part of #10043
Closes #10164

BREAKING CHANGE:
- Semantics and name of `@AppModule` (now `@NgModule`) changed quite a bit.
  This is actually not breaking as `@AppModules` were not part of rc.4.
  We will have detailed docs on `@NgModule` separately.
- `coreLoadAndBootstrap` and `coreBootstrap` can't be used any more (without migration support).
  Use `bootstrapModule` / `bootstrapModuleFactory` instead.
- All Components listed in routes have to be part of the `declarations` of an NgModule.
  Either directly on the bootstrap module / lazy loaded module, or in an NgModule imported by them.

modules/@angular/compiler/test/ng_module_resolver_mock_spec.ts

@@ -0,0 +1,46 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {beforeEach, ddescribe, describe, expect, iit, it, inject,} from '@angular/core/testing/testing_internal';
+
+import {stringify, isBlank} from '../src/facade/lang';
+import {MockNgModuleResolver} from '../testing';
+import {NgModule, NgModuleMetadata, Injector} from '@angular/core';
+
+export function main() {
+  describe('MockNgModuleResolver', () => {
+    var ngModuleResolver: MockNgModuleResolver;
+
+    beforeEach(inject([Injector], (injector: Injector) => {
+      ngModuleResolver = new MockNgModuleResolver(injector);
+    }));
+
+    describe('NgModule overriding', () => {
+      it('should fallback to the default NgModuleResolver when templates are not overridden',
+         () => {
+           var ngModule = ngModuleResolver.resolve(SomeNgModule);
+           expect(ngModule.declarations).toEqual([SomeDirective]);
+         });
+
+      it('should allow overriding the @NgModule', () => {
+        ngModuleResolver.setNgModule(
+            SomeNgModule, new NgModuleMetadata({declarations: [SomeOtherDirective]}));
+        var ngModule = ngModuleResolver.resolve(SomeNgModule);
+        expect(ngModule.declarations).toEqual([SomeOtherDirective]);
+      });
+    });
+  });
+}
+
+class SomeDirective {}
+
+class SomeOtherDirective {}
+
+@NgModule({declarations: [SomeDirective]})
+class SomeNgModule {
+}