Fixes 'URI formats are not supported' error thrown by GetDirectoryName

[vincentsels]

The GetDirectoryName function in GetPhysicalSiteRootPath kept throwing an error saying "URI formats are not supported". First stripping the execution path of its file:/// prefix, before passing it to the GetDirectoryName method, seems to fix this. Also, this path was first stored in a variable, but afterwards in the foreach loop, it was retrieved again, the path variable is hence not used. Not sure if that is intentional ? I now use the variable inside the foreach loop.

Finally, I added automatic Nuget package restore in the solution, not sure if that was allowed or not.