Feature/fog provider aws support

This is the first version of AWS support for the `fog_provider` plugin. For EC2 classic, you must specify the security_groups under Advanced (use default, if you don't know). For VPC, you must specify the security_group_ids, subnet_id, and allocate_public_ip under Advanced. Fixes #22 
minor, but we should standardize across options & providers whether we repeat provider name in label/tip.  It looks like mostly we've done label: "Region" and tip: "AWS Region"