Update sites.yml - #20

These should probably both be opt-in options rather than defaults.

@otakup0pe I think that's exactly what this does? @wgregorian would you mind also updating the documentation/readme and defaults (should be empty hashes) to reflect this change in the PR?

@pjan I was reviewing my changes from 5 months ago, I believe the defaults are already in place in README for this PR since it re-uses all existing vars. Have I missed something really obvious?

I've added a similar change for myself but introduced a variable enabled_sites. Which links from sites-available to sites-enabled based on the name entry.
But you wouldn't have to delete the while site definition if you want to disable the site.
What you think about this?

I would also prefer the distinction between enabled and available sites to be represented by different variables.

Ability do enable/disable sites was introduced with #27.
What do you think about creating the directories for the enabled sites?
In my opinion this should be handled by the deployment process of the site and not by this nginx role. Also the desired path could differ from {{nginx_www_dir}}/{{item.server.name}}
@pjan @otakup0pe

closing this in favour of #29