Fixed a bug on Catalog. `__setitem__` was not updating the translator comments. Thanks pjenvey! Fixed a bug on the `new_catalog` and `init` frontends, we were badly building the new directory for the localized catalog. Normal directory hierarchy is `<output_dir>/<locale>/LC_MESSAGES/<domain>.po`, not `<output_dir>/<locale>/<domain>.po`, ie `LC_MESSAGES/<locale>/<domain>.po`.