IUrlHelper and IViewComponentHelper need to be activated

* Removing Init method and using [Activate] to activate IUrlHelper.
* Moving IViewComponentHelper to default injected properties
* Adding functional tests to verify these properties are injected \
  activated

Fixes #789
One of these tests needs to verify that the UrlHelper can actually access the ambient values. Putting `@Url.Action()` in the razor page should suffice. 

Likewise, I don't see anywhere that view component helper is used in these tests.