feat(browser): use AppModules for bootstrap in the browser

This introduces the `BrowserModule` to be used for long form
bootstrap and offline compile bootstrap:

```
@AppModule({
  modules: [BrowserModule],
  precompile: [MainComponent],
  providers: […], // additional providers
  directives: […], // additional platform directives
  pipes: […] // additional platform pipes
})
class MyModule {
  constructor(appRef: ApplicationRef) {
    appRef.bootstrap(MainComponent);
  }
}

// offline compile
import {bootstrapModuleFactory} from ‘@angular/platform-browser’;
bootstrapModuleFactory(MyModuleNgFactory);

// runtime compile long form
import {bootstrapModule} from ‘@angular/platform-browser-dynamic’;
bootstrapModule(MyModule);
```

The short form, `bootstrap(...)`, can now creates a module on the fly,
given `directives`, `pipes, `providers`, `precompile` and `modules`
properties.

Related changes:
- make `SanitizationService`, `SecurityContext` public in `@angular/core` so that the offline compiler can resolve the token
- move `AnimationDriver` to `platform-browser` and make it
  public so that the offline compiler can resolve the token

BREAKING CHANGES:
- short form bootstrap does no longer allow
  to inject compiler internals (i.e. everything 
  from `@angular/compiler). Inject `Compiler` instead.
  To provide custom providers for the compiler,
  create a custom compiler via `browserCompiler({providers: [...]})`
  and pass that into the `bootstrap` method.

modules/playground/src/bootstrap.ts

@@ -50,12 +50,10 @@ declare var System: any;
       System.config({
         map: {'index': 'index.js', '@angular': '/all/@angular'},
         packages: {
-          // 'app': {
-          //   main: 'index.js',
-          //   defaultExtension: 'js'
-          // },
+          'app': { defaultExtension: 'js' },
           '@angular/core': {main: 'index.js', defaultExtension: 'js'},
           '@angular/compiler': {main: 'index.js', defaultExtension: 'js'},
+          '@angular/router': {main: 'index.js', defaultExtension: 'js'},
           '@angular/common': {main: 'index.js', defaultExtension: 'js'},
           '@angular/platform-browser': {main: 'index.js', defaultExtension: 'js'},
           '@angular/platform-browser-dynamic': {main: 'index.js', defaultExtension: 'js'}