Update to Rails 5.1
Fixes #21921 - Upgrade rubocop to 0.51
Fixes #19694 - Align rubocop configuration with foreman-core
And fix offenses
Fixes #12681 - Support rubocop 0.35.1 by fixing broken rules
Fixes #9708 - Fixing rubocop config so it can be used with houndci
Fixes #9159 - Fix rubocop 0.28.0 errors
Refs #7977 - Adjusting class length check in rubocop
Refs #7642 - Refactor image/tag and tests
Refs #7642 - Create docker image and tag models
Fixes #7977 - Enabling rubocop for foreman-docker
Rubocop support and config