Report virtual path consistently between file.Resolvers

[wagoodman]

The VirtualPath element is sometimes populated in the directory resolver and othertimes (when it matches the RealPath) it is not populated. This field should always be populated and if there is a presentation reason to not show one for duplication reasons (which probably should not be the case) then this should be done in the presentation layer (when rendering the final format).

[wagoodman]

Example (TODO: demonstrate with code example):

Sometimes you get this:

Location {
  RealPath: "/path/to/a"
  VirtualPath: "/path/to/a"
}

Othertimes you get this:

Location {
  RealPath: "/path/to/a"
  VirtualPath: ""
}

Depending on what file resolver you're using. This should be consistent across resolvers and the virtual path should always be provided (in my opinion) so that consumers can depend on it.