Fix bugs discovered during integration testing

* Any constructor overriding ApiBase#__construct can only extend its
  signature as API classes are always constructed with parameters for
  ApiBase#__construct
* Disabling the \Vimeo\ABLincoln\Experiments\SimpleExperiment
  constructor meant that the $name property, amongst others, wasn't
  initialised
Add the mw.PlanOut class
Register the PHPUnit unit tests properly