Switch all the HTML-based reporting modes (the internal httpd, the CGI

Switch all the HTML-based reporting modes (the internal httpd, the CGI
mode and the dump of static HTML files) to using URIs and filenames
based on the text of the pathname being reported on, rather than its
numeric index in the data file. The aim is that sub-URIs should remain
valid when the data is updated - if, for instance, you're running the
agedu CGI script permanently and changing the data file under it every
so often.

There's code in there to support the old numeric index behaviour, but
currently no UI to enable it. There could be easily enough, though.

git-svn-id: svn://svn.tartarus.org/sgt/agedu@9150 cda61777-01e9-0310-a592-d414129be87e