Allow to print ubuntu sandbox repos list and pinning rules
Allow to print ubuntu sandbox repos list and pinning rules

Add target to get the content of files from ubuntu sandbox:
- source.list (repos)
- preferences (pinning)

Change-Id: I918516857753c5caca48c4c9f71866df817fde1d

SmartInfrastructures/fuel-main-dev,teselkin/fuel-main,eayunstack/fuel-main,AnselZhangGit/fuel-main,teselkin/fuel-main,eayunstack/fuel-main,AnselZhangGit/fuel-main,teselkin/fuel-main,SergK/fuel-main,huntxu/fuel-main,teselkin/fuel-main,eayunstack/fuel-main,stackforge/fuel-main,SergK/fuel-main,SmartInfrastructures/fuel-main-dev,stackforge/fuel-main,huntxu/fuel-main,SmartInfrastructures/fuel-main-dev,AnselZhangGit/fuel-main,SergK/fuel-main,AnselZhangGit/fuel-main,huntxu/fuel-main,stackforge/fuel-main,SmartInfrastructures/fuel-main-dev