Xcode 6 support

Initial set of commits which add Xcode 6 support.
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Major changes (in xctool and Xcode 6):
- SimulatorHost framework is replaced with CoreSimulator.
- XCTest framework is moved to new folder `Platforms/iPhoneSimulator.platform/Developer/Library/Frameworks`.
- Implementation of `SimulatorInfo`, `SimulatorWrapper` is split into 2 different versions and xctool choose the correct one in runtime.
- otest-shim now redirects its output (stdout, stderr) to files which paths are provided in environment (`OTEST_SHIM_STDOUT_FILE` and `OTEST_SHIM_STDERR_FILE`) - only for iOS application tests.
- `[*TestProbe specifiedTestSuite]` is replaced with `[*TestSuite allTests]` to query list of tests because of *Test framework changes in iOS8.
- Minor changes in xcconfig files.
- Other small fixes.