- Introduce `InjectionToken<T>` which is a parameterized and type-safe
  version of `OpaqueToken`.
DEPRECATION:
- `OpaqueToken` is now deprecated, use `InjectionToken<T>` instead.
- `Injector.get(token: any, notFoundValue?: any): any` is now deprecated
  use the same method which is now overloaded as
  `Injector.get<T>(token: Type<T>|InjectionToken<T>, notFoundValue?: T): T;`.
Migration
- Replace `OpaqueToken` with `InjectionToken<?>` and parameterize it.
- Migrate your code to only use `Type<?>` or `InjectionToken<?>` as
  injection tokens. Using other tokens will not be supported in the
  future.
BREAKING CHANGE:
- Because `injector.get()` is now parameterize it is possible that code
  which used to work no longer type checks. Example would be if one
  injects `Foo` but configures it as `{provide: Foo, useClass: MockFoo}`.
  The injection instance will be that of `MockFoo` but the type will be
  `Foo` instead of `any` as in the past. This means that it was possible
  to call a method on `MockFoo` in the past which now will fail type
  check. See this example:
```
class Foo {}
class MockFoo extends Foo {
  setupMock();
}
var PROVIDERS = [
  {provide: Foo, useClass: MockFoo}
];
...
function myTest(injector: Injector) {
  var foo = injector.get(Foo);
  // This line used to work since `foo` used to be `any` before this
  // change, it will now be `Foo`, and `Foo` does not have `setUpMock()`.
  // The fix is to downcast: `injector.get(Foo) as MockFoo`.
  foo.setUpMock();
}
```
PR Close #13785
		
	
API Examples
This folder contains small example apps that get in-lined into our API docs. Each example contains tests for application behavior (as opposed to testing Angular's behavior) just like an Angular application developer would write.
Running the examples
# # execute the following command only when framework code changes
./build.sh
# run when test change
./modules/@angular/examples/build.sh  
# start server
$(npm bin)/gulp serve-examples
navigate to http://localhost:8001
Running the tests
 # run only when framework code changes
./build.sh
# run to compile tests and run them
./modules/@angular/examples/test.sh
NOTE: sometimes the http server does not exit properly and it retains the 8001 port.
in such a case you can use lsof -i:8001 to see which process it is and then use kill
to remove it. (Or in single command: lsof -i:8001 -t | xargs kill)