Last bit of refactorings

* Changed the `#define`s to be `NSString *const`s.
* Changed TestingFramework to be a dictionary rather than a class.
* Changed otest-query to look at the existence of file
  $DEVELOPER_DIR/Library/Frameworks/XCTest.framework to gate tests
  that use XCTest
* Added test project that uses XCTest and an iOS target
* Added otest-query unit test for iOS XCTest project