Add sensu_resources type that will handle resource purging

[treydock]

Pull Request Checklist

Description

Add sensu_resources type that behaves just like Puppet's built-in resources type that will handle purging unmanaged sensu types.

Related Issue

Fixes #1157

Motivation and Context

The resources collected for sensuctl types take the name of $name in $namespace to support resources with the same name in different name spaces. However it's not required to name resources that way and this causes issues with the Puppet built-in resources type which just looks at the name and nothing else. This new type looks at name plus namespace to determine if a resource exists in the catalog. The prefetching in providers that links catalog items to sensuctl items is already matching on name + namespace.

How Has This Been Tested?

I added acceptance tests for a type that supports namespaces and for a type that does not support namespaces to show the new sensu_resources type will work for both.