Allow deploys to whitelisted environments

[lewismarshall]

Currently a deploy may be deployed to any environments. This may be a problem when applications should NOT be deployed to another application's environment.

Either add a tag to a deploy:

DeployToWhitelist:
  - app_a_aceptance
  - app_a_preprod
  - app_a_prod

Or add a tag to an Environment:

WhiteListDeploys:
  - app_tier_1
  - app_tier_2