Add support for ancestor folder location for Rebracer.xml

[kzu]

It's not uncommon for a repository to contain multiple solutions at multiple directories and depths within the repo. Instead of having to maintain a plethora of Rebracer.xml files alongside each .sln, allow the extension to walk the directories up to find a settings file.

This may be a performance issues with super deep paths, but everyone knows that's a bit issue with MAX_PATH in Windows anyways so typically there aren't that many directories to traverse.