Load references as metadata

In the case of loading a single project be sure to treat references as
metadata instead of source. This prevents Roslyn from doing work that
doesn't need to be done.

Author: jaredpar

src/CodeFormatter/Program.cs

@@ -77,6 +77,7 @@ private static async Task RunAsync(string projectOrSolutionPath, IEnumerable<str
             }
             else
             {
+                workspace.LoadMetadataForReferencedProjects = true;
                 var project = await workspace.OpenProjectAsync(projectOrSolutionPath, cancellationToken);
                 await engine.FormatProjectAsync(project, cancellationToken);
             }