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/router.ts

@@ -8,8 +8,8 @@ export {Router} from './src/router/router';
 export {RouterOutlet} from './src/router/router_outlet';
 export {RouterLink} from './src/router/router_link';
 export {RouteParams, RouteData} from './src/router/instruction';
-export {RouteRegistry} from './src/router/route_registry';
 export {PlatformLocation} from './src/router/platform_location';
+export {RouteRegistry, ROUTER_PRIMARY_COMPONENT} from './src/router/route_registry';
 export {LocationStrategy, APP_BASE_HREF} from './src/router/location_strategy';
 export {HashLocationStrategy} from './src/router/hash_location_strategy';
 export {PathLocationStrategy} from './src/router/path_location_strategy';
@@ -27,41 +27,12 @@ import {PathLocationStrategy} from './src/router/path_location_strategy';
 import {Router, RootRouter} from './src/router/router';
 import {RouterOutlet} from './src/router/router_outlet';
 import {RouterLink} from './src/router/router_link';
-import {RouteRegistry} from './src/router/route_registry';
+import {RouteRegistry, ROUTER_PRIMARY_COMPONENT} from './src/router/route_registry';
 import {Location} from './src/router/location';
 import {ApplicationRef, provide, OpaqueToken, Provider} from 'angular2/core';
 import {CONST_EXPR} from './src/facade/lang';
 import {BaseException} from 'angular2/src/facade/exceptions';
 
-
-/**
- * Token used to bind the component with the top-level {@link RouteConfig}s for the
- * application.
- *
- * ### Example ([live demo](http://plnkr.co/edit/iRUP8B5OUbxCWQ3AcIDm))
- *
- * ```
- * import {Component} from 'angular2/angular2';
- * import {
- *   ROUTER_DIRECTIVES,
- *   ROUTER_PROVIDERS,
- *   RouteConfig
- * } from 'angular2/router';
- *
- * @Component({directives: [ROUTER_DIRECTIVES]})
- * @RouteConfig([
- *  {...},
- * ])
- * class AppCmp {
- *   // ...
- * }
- *
- * bootstrap(AppCmp, [ROUTER_PROVIDERS]);
- * ```
- */
-export const ROUTER_PRIMARY_COMPONENT: OpaqueToken =
-    CONST_EXPR(new OpaqueToken('RouterPrimaryComponent'));
-
 /**
  * A list of directives. To use the router directives like {@link RouterOutlet} and
  * {@link RouterLink}, add this to your `directives` array in the {@link View} decorator of your