Bugfix/gzip

[jaboja]

• I've fixed the gzip responses, which seemed to get wrong when the chunked transfer encoding was also on. It may however still need some work, to make the gzip chunked, and not just avoid doing a chunked response when it's gzipped.
• I've also fixed the MIME type for GET responses for directories, as the httpd/unix-directory makes no sense with a HTML listing of a directory.
• And as an alternative to those listings, I've added support for index.html files. It requires defining the name(s) of the index file(s), however, and by default is disabled.