edx-west/{prod,stage}-jumpbox: barebones playbooks

Just to facilitate user updates to the jumpboxes.
Merge pull request #254 from edx/sef/edx-west-jumpboxes

edx-west/{prod,stage}-jumpbox: barebones playbooks
Rename edx-platform version variables
Merge pull request #257 from edx/db/rename-version-vars

Rename edx-platform version variables
Merge branch 'master' of https://github.com/edx/configuration