Remove the refs/tags seperation.

Instead, we take any extra_vars that have a suffix of '_version' and
make sure those exist as tags on the AMI. All other vars do not get
saved anywhere.

Turn on instance tagging with abbey.
Optionally tag instances when roles deploy code.

The instance gets tagged with the repo and hash that was deployed.
Move from ec2.yml to tag_ec2.yml
Merge pull request #1262 from edx/feanil/abbey_gitrefs

Feanil/abbey gitrefs