Allow the use of wls_server arguments as arrays

As I've been using this module, I found myself repeating quite a lot of server arguments in my YAML files, and this annoyed me. YAML allows the use of so-called ["alias nodes"](http://www.yaml.org/spec/1.2/spec.html#id2786196), which I like to call *references*. By allowing the use of arrays, I can use one instance of a server argument as an *anchor*, and in all subsequent uses of that argument, I simply reference that anchor!

**NB**:It's still possible to use a scalar value as the value for wls_server arguments!