[Runtime] Enable the folder based i18n support for WGT package.

The WGT folder based i18n support based on system locale setting and
application default locale setting (in config.xml), this patch will
enable to load resources by these locale settings.

For more details, please refer to
http://www.w3.org/TR/widgets/#folder-based-localization

The related bug is https://crosswalk-project.org/jira/browse/XWALK-1030