Add the possibility to set custom templates for some files
This can be done with the PagesTemplates configuration variable,
that lists couples (page name -> template to use)

A template for org-mode documents generated with mlorg is provided
Explicitely compile with Str
Documents that match a template can now be specified using a regexp
Removing the -e option for echo, that isn't supported by dash
Do not fail if the default templates are not here.
It is for example useful for previous installations of stone where the
org-template do not exist
Using printf instead of echo to be fully POSIX compatible