E3-226: POSIX compliant directory names for autosave directories

See https://jira.esss.lu.se/browse/E3-226 for context.

One thing I'm doubtful about here is the necessity of changing the version of the module, since this definitely constitutes an API-breaking change per the SemVer scheme - but we haven't modified the underlying (wrapped) module.

I do notice that a build number already is appended to the version number here, which makes me even more confused - should these ever be commited to git, and should I be bumping it? (I.e., the question from last week - is this even a "build" number?)