feat(core): provide support for relative assets for components

Assets defined for `templateUrl` and `styleUrls` can now be loaded
in relative to where the component file is placed so long as the
`moduleId` is set within the component annotation.

Closes #5634

tools/broccoli/trees/browser_tree.ts

@@ -49,6 +49,7 @@ const kServedPaths = [
   'playground/src/http',
   'playground/src/jsonp',
   'playground/src/key_events',
+  'playground/src/relative_assets',
   'playground/src/routing',
   'playground/src/sourcemap',
   'playground/src/svg',