Read passwords from redirected input

Add a fallback to allow reading passwords from redirected input.  This is
beneficial for scripts that don't want to expose the password in the command
line arguments.

DepotDownloader/Program.cs

@@ -159,8 +159,17 @@ static bool InitializeSteam( string username, string password )
                 do
                 {
                     Console.Write( "Enter account password for \"{0}\": ", username );
-                    password = Util.ReadPassword();
-                    Console.WriteLine();
+                    // Avoid console echoing of password
+                    try
+                    {
+                        password = Util.ReadPassword();
+                        Console.WriteLine();
+                    }
+                    // Fallback to support redirected input
+                    catch ( System.InvalidOperationException )
+                    {
+                        password = Console.ReadLine();
+                    }
                 } while ( String.Empty == password );
             }
             else if ( username == null )