[WIP] Rails 4 upgrade

**DO NOT MERGE YET, WORK IN PROGRESS!**

To get some first feedback I'm already creating this pull request. Of course we will cleanup the commits when it's done for merging.

There will me multiple barclamp pull requests linked against this pull request.
Are you 100% sure we don't need rubygem-ruby-shadow anymore? I thought it's still needed by chef when using a resource to change a user password?