Implemented support for better dealing with test arguments defined in Xcode schemes. Arguments strings are correctly separated into multiple arguments respecting spaces, quotes and escaped quotes.
This should fix Issue #234: xctool wrongly separates "Arguments passed on launch" defined in scheme

More work on #234:
- Adjusted coding style
- Improved argument parsing to deal with more edge cases
- Combine all active argument lines from scheme into one virtual line so that quoting across lines is possible.
- Moved argument parsing to XCToolUtil
- Implemented test for argument parsing cases in XCToolUtilTests
- Restored previously changed scheme test cases

More coding style adjustments.

More work on #234:
To be able to correctly deal with single and double quotes and their various nested combinations, I switched the implementation to a single-pass state machine-like approach. To my mind, it is more concise at may be adjusted more easily should we find more edge cases in Xcode.