refactor(core): change module semantics

This contains major changes to the compiler, bootstrap of the platforms
and test environment initialization.

Main part of #10043
Closes #10164

BREAKING CHANGE:
- Semantics and name of `@AppModule` (now `@NgModule`) changed quite a bit.
  This is actually not breaking as `@AppModules` were not part of rc.4.
  We will have detailed docs on `@NgModule` separately.
- `coreLoadAndBootstrap` and `coreBootstrap` can't be used any more (without migration support).
  Use `bootstrapModule` / `bootstrapModuleFactory` instead.
- All Components listed in routes have to be part of the `declarations` of an NgModule.
  Either directly on the bootstrap module / lazy loaded module, or in an NgModule imported by them.

modules/@angular/compiler/src/directive_resolver.ts

@@ -33,7 +33,7 @@ export class DirectiveResolver {
   /**
    * Return {@link DirectiveMetadata} for a given `Type`.
    */
-  resolve(type: Type): DirectiveMetadata {
+  resolve(type: Type, throwIfNotFound = true): DirectiveMetadata {
     var typeMetadata = this._reflector.annotations(resolveForwardRef(type));
     if (isPresent(typeMetadata)) {
       var metadata = typeMetadata.find(_isDirectiveMetadata);
@@ -42,8 +42,10 @@ export class DirectiveResolver {
         return this._mergeWithPropertyMetadata(metadata, propertyMetadata, type);
       }
     }
-
-    throw new BaseException(`No Directive annotation found on ${stringify(type)}`);
+    if (throwIfNotFound) {
+      throw new BaseException(`No Directive annotation found on ${stringify(type)}`);
+    }
+    return null;
   }
 
   private _mergeWithPropertyMetadata(