Allow installing Xcode with Additional Tools

[martin-braun]

There are additional tools for each Xcode version. It would be nice to have the ability to install those as well when installing an Xcode version.

This should also be added to the GUI application.

I think it would make sense to just put them into the App Package somewhere, so version switching through renaming would allow aliases to the tools that are compatible to the current Xcode version. I've put them into /Applications/Xcode.app/Tools and it works flawlessly.

Thanks!