promotion - remove legacy promotion in the UI

This commit contains changes to remove the legacy
promotion of products/repos/packages/errata/distributions
from the UI (only).  After this change, the only content type
that may be promoted is content views.

Note: This is an ammended commit.  Previously it had also removed
actions from the errata and packages controller that were no longer
used, as well as the view partials on those controllers.  Based on
pull request feedback, we will leave those in place to be reused/
modified when logic is added to content search.  At that time,
we can remove those files, if no longer needed.  Files involved
included:
   app/controllers/errata_controller.rb
   app/controllers/packages_controller.rb
   app/views/errata/_packages.html.haml
   app/views/errata/_show.html.haml
   app/views/packages/_changelog.html.haml
   app/views/packages/_dependencies.html.haml
   app/views/packages/_filelist.html.haml
   app/views/packages/_show.html.haml
delete-legacy-promotion - ui/model - make view required for system and akey

This commit contains changes so that content view is required
for systems and activation keys.  Previously, the user could
assign systems/keys an environment, but omit the view.