Started new multi-language feature

Added a new resource file default.yml that contains the strings.
Added a header in the configuration file.
Cleaned code in YamlStorage.
Updated to 1.8.4b for developpement.
Separated the strings class into the storage class and the strings loader.

Creating a default.yml file in the folder if there's no file.
Deprecate the old loadStrings() method.
Catch some errors that could happen when loading the strings.

Added a new string.
Code cleanup.