When attempting to determine the location of the DAUX configuration
file, also check the REDIRECT_CONFIG_FILE environment variable.  This
allows you to have multiple Daux "books" running from a single
Daux installation.

To do this, create your Daux md files in a dedicated directory,
and create a .htaccess file in that directory that looks like this:

RewriteEngine On
RewriteBase /daux/

SetEnv CONFIG_FILE      /home/myself/my-book-path/book-config.json

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* index.php [L,QSA]
RewriteRule .* - [E=CONFIG_FILE,F]