web/username_prefix.php: user2path(): comment prefixes: documented how to put the comment on a separate line when word-wrapping (c-_:x@url). this format works in Google spreadsheets.

web/username_prefix.php: user2path(): added support for comment prefixes, which can be used to include term categories. note: when URL is used without http:// , you must include a non-letter in the comment (eg. c_:x@url) to work in Firefox.

web/username_prefix.php: user2path(): visually separated steps for easier readability

bugfix: web/username_prefix.php: user2path(): padding used to visually separate 1st element of URL: require all padding to be __ because sometimes terms contain a leading or trailing _

bugfix: web/username_prefix.php: user2path(): padding used to visually separate 1st element of URL: support embedded @ inside highlighted part: also need to match end-padding when followed by "."

web/username_prefix.php: user2path(): padding used to visually separate 1st element of URL: support embedded @ inside highlighted part

web/username_prefix.php: user2path(): added support for padding used to visually separate 1st element of URL (x@url -> x@url)

bugfix: web/username_prefix.php: need to handle : in login (which would normally indicate a password)

web/.htaccess: auto-detect dotpath: need to explicitly set usernames_disabled=1, because for some reason the `%{QUERY_STRING} =""` check doesn't detect a query string

web/.htaccess: auto-detect dotpath: removed handling of no longer used @ prefix (used to be used by username-based prefix subpaths)