feat(di): provide two ways to create an injector, resolved and unresolved

Add two factory static functions to Injector: resolveAndCreate and
fromResolvedBindings.

We want to avoid resolution and flattening every time we create a new
injector. This commit allows the user to cache resolved bindings and
reuse them.

modules/angular2/src/core/compiler/view.js

@@ -153,7 +153,7 @@ export class AppView {
       if (isPresent(componentDirective)) {
         var injectables = componentDirective.annotation.injectables;
         if (isPresent(injectables))
-          shadowDomAppInjector = appInjector.createChild(injectables);
+          shadowDomAppInjector = appInjector.resolveAndCreateChild(injectables);
         else {
           shadowDomAppInjector = appInjector;
         }