these used to be in one directory called 'templates' (as they used to
be grouped in a separate repository together) but now are referenced
separately, alongside the inventory

in addition, both the roles and include areas are added to the Jinja2
environment at the toplevel, meaning they no longer need a preceding
'roles/' or 'include/' directory prefix, when used in files

the old '-t' option has been split into '-r' (roles) and '-n' (include)
directory options

removed the -a ('add templates') command line option as that serves no
purpose now either can be changed separately (it was used to add more
roles, but they can just be overridden; there is no way to add extra
includes, but that shouldn't be necessary)