Fix CONFIG_START/CONFIG_END

Sets up KWConfigurationTestObserver in +[KWExampleSuiteBuilder initialize] to 
respond to -[XCTestObserver startObserving] and -[XCTestObserver
stopObserving].

Also moves TestSuiteConfigurationAdditions into the SenTestingKit
subdirectory, and removes it from the XCTest static lib, to disable the method
swizzling implementation under XCTest.


A patch is pending here (just needs some testing and tidying up). I don't think
SenTestingKit support should be completely dropped in a minor release, so I'd
still like to have this fixed for v2.3.0.