Allow configurable ResourceController implementations.

This allows a different class to be specified to replace
PhlyRestfully\ResourceController when constructing controllers through
the factory.  A restriction is kept to ensure that the replacement
controller extends the original controller.

This allows users of PhlyRestfully to further configure the behaviour of
the controller if necessary.

* Modification to default configuration add a new "controllerClass"
  parameter, defaulting to the current ResourceController.
* Modification to the factory to construct the specified class instead
  the hard coded PhlyRestfully\ResourceController.