fixes #2407 - Add STI to settings model

Also adds some tests for rendering new/missing STI models, and
refactors the old default_settings loader into the new sub-models.
fixes #2430 - undefined method gettext_translation_for_attribute_name
Added rails and dependencies to comp
fixes #2428 - a workaround for an issue with SETTINGS[:libvirt] not being properly initialized in rpm environments
Fixes #2433 - Fix Orchestrastion resond_to? test to work on ruby 2.0