Fixed typo

Common/ConfigFileManager.cs

@@ -55,7 +55,7 @@ public static class ConfigFileManager
                 }
                 else
                 {
-                    throw new InvalidConfigurationException("One or more required fileds were missing from the configuration file.");
+                    throw new InvalidConfigurationException("One or more required fields were missing from the configuration file.");
                 }
             }
             else