Add custom facts

[bobtfish]

Puppet by default provides not all that many AWS facts for instances.

Add at least facts to determine region/AZ etc.

[clarabstract]

I am in the process of adding exactly this actually :)

e: Oh you have them already! Ok I'll wait for you to merge instead.

[clarabstract]

Just a note on this - I'm trying very hard in my refactors to avoid looping over regions as it is incredibly slow (and filtering them out via an ENV var is a little hackish to say the least). So rather than adding AZ info as a fact (which is always evaluated) I thought I'd just provide a lookup function (given region, return AZs).