Adding Nginx routing SPI for HA applications

@andrewklau https://docs.puppetlabs.com/puppet/latest/reference/lang_containment.html is a good start, I had to do a deep dive into this recently to resolve some ordering conflicts that we were seeing.

For the anchor pattern:
The problem that comes into play is that while you can do resource ordering based on classes to ensure that one class is completed before another, however this only ensures the ordering of the declared resources in each of the classes. Any included classes within those classes are not bound to that ordering. Puppet >= 3.4 has the contain function which allows this, but since we need to maintain compatibility for older versions of puppet, we need to use the anchor pattern to achieve the same type of dependency ordering.

The ensure_resource function from stdlib is similar in that it suffers from parse ordering issues: http://grokbase.com/p/gg/puppet-users/143zzr9kx5/is-ensure-resource-evil