Use php-gettext (developpement version rev43, because of php5.3) as fallback
Use native language (english) instead of key for translation
Keep directory en_UK for english customization
Need some refactoring for plurals
Todo : managing plugins in the same way
git-svn-id: http://piwigo.org/svn/trunk@5021 68402e56-0260-453c-a942-63ccdbb3a9ee
