toastergui: dirinfo needs path separation

toastergui: dirinfo needs path separation

In the dirinfo URLs we use the "/" separator for directory
separation which coincides with the "/" separator in HTTP URIs.

This is not a problem, but we must not have consecutive "/"
characters as the web servers will conflate those - we add
a "_" delimitator to separate the Django managed URL from the
dirpath parameter, while maintaining the unique ID of REST urls.

Signed-off-by: Alexandru DAMIAN <alexandru.damian@intel.com>