Refactor the way the server properties work

Hi! I wanted to make the way that we set minecraft server properties a bit more flexible. So I cracked it open and came up with this. 

Some key side-effects you'll notice is that the properties are separated into their own "namespace" of sorts in the cookbook attributes. I think the win here is readability and separation of concerns in the configuration of the cookbook. Also, in this refactor we have a cleaner template, and a more flexible way to define server properties.

Thoughts on this?