TODOS

- Adding support for integration with AppDB for images
    + Images are specify with parameter "--appdb <image name/ID in AppDB>"
    + The client will replace the parameter with "--image imageID" before calling OpenStack client (like site and VO)

- Caching keystone token, reuse it for successive OpenStack commands without authentication via CheckIn again
    + Make a dict: key = hash of (site + vo + access token), value = keystone token
    + Before using OpenStack command, check the dict reuse the token if found. If not found, generate new token
    and add it to the dict.
    + Applicable only for using as library

- Check last commit and update site configuration