conf: Moved "default_mimetype" configuration constant from conf/app/server.py to conf/mimetypes.py. (Used by fileservice now too, so general). fileservice: Now guesses mimetype of files being served instead of serving them all with the same mimetype. The Content-Type returned will be used by file browser for viewing certain types of files. server: Fixed directory problem (previously served with just a "0"). Now directories return a 403 Forbidden error. (Not allowed to browse directories since this is viewable by the public).