Move 'php5' nginx config to separate template

Options for PHP5 support in the generated nginx server configuration
files are moved to a separate template which extends 'default.conf.j2'.

Websites that require PHP5 support will need to have 'item.type: "php5"'
in their configuration hash to use new template instead of the default
one.
Remove templated nginx fastcgi_params

I'm switching to use packaged version if /etc/nginx/fastcgi_params
configuration file. This patch will restore the original file by
disabling the diversion and create temporary "diverted" file to not
cause nginx error on playbook run.

Temporary tasks will be removed in the future after all servers are in
a correct state.
Update CHANGELOG.md
Merge pull request #123 from drybjed/role/nginx

Updates in 'nginx' role