Add support for installing php-fpm with nginx

This is based on the assumption that when using the `magento::nginx` recipe you're going to also want to install `php-fpm`. This is our use case.

1. Removes the dependancy on external `php-fpm` cookbooks of varying quality. Installs `php-fpm` from distro packages.
2. Uses the same base php.ini for both `php-cgi` (command line) and `php-fpm`.
3. _Very_ simple implementation.
4. Fixes a couple of bugs as noted below.