jLocale: new mapping directory to ease the translation of locales

The application can now have a var/locales/ directory where you
can put properties files overriding existant files, or properties
file for a new language.

var/locales/<lang>/<module>/locales/<properties file>

It's better thant var/overloads/ because to provide a new
language, you just have to provide a zip containing file and
extract files into var/locales/.
The createlangpackage generates now locales into the new locales/ directory layout
jLocale: It's better to have higher priority on overloads/

in this case, we can overrides locales that are provided in var/locales