Refactoring: $smarty, $Config in Context, lang_* in Language class.

[ Previous state ]

• $smarty is already in context but still were initialized in index.php
• $Config are global variables
• L10n code uses lang_* global functions
• The default message fallback language were MESSAGE_FALLBACK_LANG

[ New state ]

• Smarty init code is now in Context::initializeTemplateEngine()
• The configuration is Context::$config.
• A language class contains the L10n logic and lang_* are moved here
• The default message fallback language is Language::FALLBACK

[ Notes ]

• As we don't have a loader for the context, we're keeping temporarily the $Config global variable array, so we can refactor static methods depending of the configuration to ask a context.

[ Feature description ]

Current