Currently, there is a single flag COMMON_ENABLE_BASIC_AUTH to decide whether to
enable basic auth in the nginx config.  This change allows to enable basic auth
selectively for individual services.

By setting NGINX_ENABLE_SSL ssl this will be enabled in
the nginx configuration for those roles that support
it, currently just the lms and cms.

To use a custom key/cert set the following vars:

* NGINX_SSL_CERTIFICATE
* NGINX_SSL_KEY

Note that there is only one ssl certificate and key
per nginx install, this is because of the way nginx
is setup (independent of the other roles).

We could enable it for different roles though they would
share the same certificate.

Instead of enabling basic auth per role this makes it
an nginx parameter which makes more sense for sandboxes
and probably other servers where we want basic auth turned on

Conflicts:
	playbooks/roles/common/handlers/main.yml

removing nginx setup from individual roles

If the nginx play is called with the nginx_conf varialble, then expect
to find in {{secure_dir}}/files/nginx.conf and copy it over.  If not set
then the default one already there will be sufficient.

One comes with the standard installation, overwrite with our own,
provided in {{secure_dir}}/files.