fix cors problems

ClusterController is a child class of ObjectController
it needs to have the same instance properties
because the instance is created by middleware and not the Proxy Application __init__ was not called with proper arguments
sometimes it worked (because middleware has some properties of Proxy App), sometimes not
now the __init__ is called correctly and all the methods of the parent class should work as expected

cors wrapper `cors_vaidation` was using references to Proxy App in the controller code
when properties were restored `cors_validation` started working as expected

take note, that `test_cors()` test case has some commented out code
it's because of bug in Swift (fixed in current master, cannot really find a specific commit, for some reason) and is not fixed in 1.13.1, which we use for testing and deploy
you can easily test it by checking out `master` and `1.13.1` and running the commented out test on both
Merge pull request #68 from pkit/bug_fix

fix cors problems