Use Component::initialize() instead of overriding constructor.

Component::initialize() has been updated in CakePHP 3 to match other initialize() methods.
As per cakephp/cakephp#4823

Also update are the various tests that were affected by this change, including the changing of the AddActionTest to use the IntegrationTestCase. This was necessary to get the API tests to pass (The other Action tests are not affected by this since they do not use the API listener)
Thanks, that makes things way easier. I did not realise that I could just use `beforeFilter`.