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/forms/src/directives.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Type} from '@angular/core';
+import {NgModule, Type} from '@angular/core';
 
 import {CheckboxControlValueAccessor} from './directives/checkbox_value_accessor';
 import {DefaultValueAccessor} from './directives/default_value_accessor';
@@ -83,3 +83,10 @@ export const FORM_DIRECTIVES: Type[][] =
 
 export const REACTIVE_FORM_DIRECTIVES: Type[][] =
     /*@ts2dart_const*/[REACTIVE_DRIVEN_DIRECTIVES, SHARED_FORM_DIRECTIVES];
+
+/**
+ * Internal module used for sharing directives between FormsModule and ReactiveFormsModule
+ */
+@NgModule({declarations: SHARED_FORM_DIRECTIVES, exports: SHARED_FORM_DIRECTIVES})
+export class InternalFormsSharedModule {
+}