Code fixes

app/assets/stylesheets/framework/blocks.scss

app/assets/stylesheets/framework/common.scss

app/controllers/groups_controller.rb

app/finders/contributed_projects_finder.rb

app/finders/groups_finder.rb

app/finders/joined_groups_finder.rb

app/finders/personal_projects_finder.rb

app/models/ability.rb

app/services/groups/base_service.rb

app/services/groups/create_service.rb

app/services/groups/update_service.rb

app/views/groups/show.html.haml

config/gitlab.yml.example

...3_add_default_group_visibility_to_application_settings.rb

lib/gitlab/current_settings.rb

lib/gitlab/visibility_level.rb

spec/features/security/group/internal_access_spec.rb

spec/features/security/group/private_access_spec.rb

spec/features/security/group/public_access_spec.rb

spec/finders/groups_finder_spec.rb