[WIP] Build OpenProject release 3.0.X deb package via packager.io

This PR is not meant to be merged right now. It is created for early testing on travis only. 
@tessi the idea is that in production you would always have RAILS_ENV set to `production`. So there is no need to set it here or at least you can set it to `development` here. By doing so you don't have to care about this in `development`, which is a very developer friendly approach. I like it and I suggest we leave it as is.