Move blocks' opening curly bracket on a new line

Setting breakpoints is much easier this way
Set the project class prefix to `XCD`
More consistent documentation of error codes
Update restricted video error description
Update video identifier of geoblocked test video
Add possibility to run tests in online mode
Add unit test for age restricted video
Better fix for invalid certificates in unit tests
Add script phase for deleting *.gcda files

This gets rid of the "profiling:invalid arc tag" logs when running unit tests

* Add script phase in both iOS and OS X unit tests targets
* See http://stackoverflow.com/questions/22519530/dozens-of-profilinginvalid-arc-tag-when-running-code-coverage-in-xcode-5/22976101#22976101
Fix typo in CHANGELOG
Support for age restricted videos
Cleanup XCDYouTubeKit OS X scheme
Run XcodeCoverage’s exportenv.sh script if found

XcodeCoverage will be all set up by just making a symbolic link to the `XcodeCoverage` directory at the root of this project.