start creation of nginx role

* install the package
* enable the service
* make sure it's running
* copy nginx.conf file to templates/ directory
* render the template
* add a handler to reload nginx in case its configurations files are
  changed
split nginx configuration file

* add a new variable nginx_log_dir, the base directory for storing logs
  for nginx servers
* make sure this directory exists
* make nginx read {{nginx_conf_dir}}/conf.d for extra configuration
  parameters
* make nginx read {{nginx_conf_dir}}/sites-enabled for server
  configurations
* extract a server configuration that can be used as a template for
  creating new server configurations (or for checking that basic
  installation of nginx works)
* make nginx by default to use all available cores
finalise nginx role

* add two templates:
  proxy
    reverse-proxy setup

  static
    static web site setup
* add tasks to
  * create corresponding log directory
  * create corresponding server configuration file
create and use a spool directory not in /tmp

* use it for proxy temporary files
make a local copy of `getent` module

Original is at https://github.com/ansible/ansible-modules-extras/blob/devel/system/getent.py
add an account for non-privileged tasks/services

* comment the purposes of service_account and worker_account
fix the local.yml

* add loading of secrets
* fix the name of the first task
put nginx logs in the same place where other nginx logs are to be found
rename sites-enabled to just sites
add documentation for the nginx role
Merge pull request #38 from sa2ajj/goodies

Goodies