Allow modules to include a module_exports.lua file in their root which
will cause the file save/modules/module_name.lua to be generated
pointing to the exports file.
Map locale files located at locale/{lang}/{file} in a module to
locale/{lang}/{module-name}-{file} in the save. This additionally
support a shorthand notation by mapping locale/{lange}.cfg to
locale/{lang}/{module-name}.cfg.
Resolves#500.