Add a way to remove nginx server configuration

In server configuration hash, you can now specify 'delete: True' to have
both the nginx server configuration generated by Ansible and link to it
removed on the next Ansible run.
Reorder some nginx tasks
Remove remnants of diverted fastcgi_params

This is the second step of the conversion from custom fastcgi_params
configuration file to the stock version.

At this point, diversion of 'fastcgi_params' configuration file should
have been removed from the server, and a dummy
fastcgi_params.dpkg-divert{,lock} files will be present instead. This
patch removes them from the server if fastcgi_params.dpkg-divert.lock
file is found.

At some later date, the task that removes the dummy config files will be
removed.
Rename 'http-default.d' dir to 'site-default.d'

New name of this directory should better reflect what it is meant for.
This directory is included in all nginx server config files that are
configured as default sites. You can for example put configuration of
subdirectories available on the default site there.
Remove 'nginx_manage_*' variables

These variables (nginx_manage_servers, nginx_manage_upstreams) are
actually redundant, easier way to disable servers and upstreams is just
to set empty lists (nginx_servers and nginx_upstreams).
Clean up upstream template naming scheme

Now all nginx upstream templates will be called in an unified format,
templates/etc/nginx/conf.d/upstream_*.conf.j2

Default upstream template has been named 'upstream_default.conf.j2'.
Add a way to remove nginx upstream configuration

If 'delete: True' key is defined in nginx upstream configuration,
resulting config file will be removed from the host if found.
Add support for nginx map { } section

More information about nginx maps can be found at
http://nginx.org/en/docs/http/ngx_http_map_module.html
Change name of the task file in nginx role
Merge pull request #3 from drybjed/nginx-updates

Many nginx updates