Implementing __set_state for CakeRoute

It helps the applications to cache the routes using var_export when possible.
Maybe I'm caffeine deficient, but this test isn't testing setState. Whether the function `CakeRoute::__set_state` is defined or not this test will pass, it's not really testing anything at all. 

_The result_ of calling `CakeRoute::__set_state` is what should be being tested.