Add framework search path with XCTest for Xcode 6 iOS simulator launch environment
Improve simulated device and sdk selecting mechanism.

Summary:
In xctool tests we are using cached output of xcodebuild -showbuildsettings. It could happen that sdk, that was originally used to generate it, i.e. iOS 6, is not available on the machine which actually runs xctool tests. In that case we could try to find the best compatible pair <simulated device, simulated iOS sdk>.
Added functions to XCToolUtil that return paths with test frameworks.
Fix duplicated test cases by reloading `isEqual:` and `hash` methods of NSInvocation.