Preparing new base functionality: 
- prefetch based on catalogued region only
- recursive region lookup in providers 
- sugar to generate region lookup
- on-demand prefetch during lookup
- sugar to generate API methods
- ruby <1.8 shim for class methods
Add region finders to all providers
Remove redundant properties (subnets imply vpcs, vpcs imply region)
Transition all existing resources to new `Aws_api` interface (`instance_from-aws` and `aws_items_for_region`) and added `primary_api` class macro to help generate the latter.