Support GetFileInfo for directories

[stilettk]

Currently GetFileInfo supports only files: when called on a path that points to a directory it returns PhysicalFileInfo which has IsDirectory == false.

So, when given a path, how to decide what to do: to call GetFileInfo (if it's a file) or call GetDirectoryContents (if it's a folder)? Currently the only way I found isn't very intuitive:
bool isDirectory = fileProvider.GetDirectoryContents(myPath).Exists

My suggestion:
new PhysicalFileProvider(myPath).GetFileInfo("data")
Expected:
PhysicalDirectoryInfo
Actual:
PhysicalFileInfo

[aspnet-hello]

This issue was moved to aspnet/Home#2537