Option to include env.cloud on deploy with migration

It has recently come to our attention that if a migration command depends on environment variables set on env.cloud, it fails miserably. To address this manually you can populate the migration text field that appears the moment you check migration with the following: 

`source /data/_appname_/shared/config/env.cloud && rake db:migrate`

addressing this on serverside could have the following outcome:

1. Remove the feeling of disappointment caused by a failed deploy (especially new customers/users)
2. Generate less support tickets that are a direct result of that