Move to a new model for data stored in redis

- Keep sets to index instances/apps/roles so it's not necessary
 to scan the keyspace using keys command all the time
- Added datahelper module and moved almost all call to redis there,
  so keys can be changed or prefixed in future without hunting for them
  everywhere
- Better tracking of unregistered servers
- Simplified rehash
- Add migrate script to convert data from old version (useful on upgrade
  and in case we want to restore an old dump)
Merge from master
Expanded helpers to deal with chef_runlist
Added dockerfile and fig.yml
Added volume to redis
Ignored fig data volume path
Added script to download backup from s3
Merge branch 'dockerize' into new_data_model
Updated migrate script to get env var from docker
Install racksh into the container
Fixed redis commandline in fig
Missing require in helper
Fix permission of volume dir
Small fixes
Merge from master
Merge from master
Add dryrun mode
Add support to set AWS keys via env var
Set dryrun for gaptool container in fig
Add entrypoint to convert env var in fig