refactor(router): improve recognition and generation pipeline

This is a big change. @matsko also deserves much of the credit for the implementation.

Previously, `ComponentInstruction`s held all the state for async components.
Now, we introduce several subclasses for `Instruction` to describe each type of navigation.

BREAKING CHANGE:

Redirects now use the Link DSL syntax. Before:

```
@RouteConfig([
	{ path: '/foo', redirectTo: '/bar' },
	{ path: '/bar', component: BarCmp }
])
```

After:

```
@RouteConfig([
	{ path: '/foo', redirectTo: ['Bar'] },
	{ path: '/bar', component: BarCmp, name: 'Bar' }
])
```

BREAKING CHANGE:

This also introduces `useAsDefault` in the RouteConfig, which makes cases like lazy-loading
and encapsulating large routes with sub-routes easier.

Previously, you could use `redirectTo` like this to expand a URL like `/tab` to `/tab/posts`:

@RouteConfig([
	{ path: '/tab', redirectTo: '/tab/users' }
	{ path: '/tab', component: TabsCmp, name: 'Tab' }
])
AppCmp { ... }

Now the recommended way to handle this is case is to use `useAsDefault` like so:

```
@RouteConfig([
	{ path: '/tab', component: TabsCmp, name: 'Tab' }
])
AppCmp { ... }

@RouteConfig([
	{ path: '/posts', component: PostsCmp, useAsDefault: true, name: 'Posts' },
	{ path: '/users', component: UsersCmp, name: 'Users' }
])
TabsCmp { ... }
```

In the above example, you can write just `['/Tab']` and the route `Users` is automatically selected as a child route.

Closes #4728
Closes #4228
Closes #4170
Closes #4490
Closes #4694
Closes #5200

Closes #5475

modules/angular2/test/router/router_spec.ts

@@ -8,7 +8,7 @@ import {
   expect,
   inject,
   beforeEach,
-  beforeEachBindings
+  beforeEachProviders
 } from 'angular2/testing_internal';
 import {SpyRouterOutlet} from './spies';
 import {Type} from 'angular2/src/facade/lang';
@@ -18,9 +18,8 @@ import {ListWrapper} from 'angular2/src/facade/collection';
 import {Router, RootRouter} from 'angular2/src/router/router';
 import {SpyLocation} from 'angular2/src/mock/location_mock';
 import {Location} from 'angular2/src/router/location';
-import {stringifyInstruction} from 'angular2/src/router/instruction';
 
-import {RouteRegistry} from 'angular2/src/router/route_registry';
+import {RouteRegistry, ROUTER_PRIMARY_COMPONENT} from 'angular2/src/router/route_registry';
 import {RouteConfig, AsyncRoute, Route} from 'angular2/src/router/route_config_decorator';
 import {DirectiveResolver} from 'angular2/src/core/linker/directive_resolver';
 
@@ -30,16 +29,12 @@ export function main() {
   describe('Router', () => {
     var router, location;
 
-    beforeEachBindings(() => [
+    beforeEachProviders(() => [
       RouteRegistry,
       DirectiveResolver,
       provide(Location, {useClass: SpyLocation}),
-      provide(Router,
-              {
-                useFactory:
-                    (registry, location) => { return new RootRouter(registry, location, AppCmp); },
-                deps: [RouteRegistry, Location]
-              })
+      provide(ROUTER_PRIMARY_COMPONENT, {useValue: AppCmp}),
+      provide(Router, {useClass: RootRouter})
     ]);
 
 
@@ -225,6 +220,11 @@ export function main() {
   });
 }
 
+
+function stringifyInstruction(instruction): string {
+  return instruction.toRootUrl();
+}
+
 function loader(): Promise<Type> {
   return PromiseWrapper.resolve(DummyComponent);
 }