refactor(core): introduce ComponentFactory.

Each compile template now exposes a `<CompName>NgFactory` variable
with an instance of a `ComponentFactory`.
Calling `ComponentFactory.create` returns a `ComponentRef` that can
be used directly.

BREAKING CHANGE:
- `Compiler` is renamed to `ComponentResolver`,
  `Compiler.compileInHost` has been renamed to `ComponentResolver.resolveComponent`.
- `ComponentRef.dispose` is renamed to `ComponentRef.destroy`
- `ViewContainerRef.createHostView` is renamed to `ViewContainerRef.createComponent`
- `ComponentFixture_` has been removed, the class `ComponentFixture`
  can now be created directly as it is no more using private APIs.

modules_dart/transform/lib/src/transform/template_compiler/generator.dart

@@ -66,7 +66,7 @@ Future<Outputs> processTemplates(AssetReader reader, AssetId assetId,
     for (var reflectable in viewDefResults.viewDefinitions.keys) {
       // TODO(kegluneq): Avoid duplicating naming logic for generated classes.
       reflectable.annotations.add(new AnnotationModel()
-        ..name = 'hostViewFactory_${reflectable.name}'
+        ..name = '${reflectable.name}NgFactory'
         ..isConstObject = true);
     }
   }