Content views: fix filter add_product error
Merge pull request #1844 from daviddavis/fix-filter-error

Content views: fix filter error message
Code to incorporate filters while publishing CVD
Added version compare facility for package rules
Added tests for the errata and package_group publishes
Fixed a couple of unit tests to make travis happy
Removed unused comments
Moved the index_package and errata calls to a single method

Added this so that we can add "index_package_groups"
in a single place instead of having to repeat it everywhere
Added infrastructure for package groups index and search
Added code to intergrate the package group to the cvd publish
Made some modifications for PackageGroupSearch
Added a default search field param to enable one to choose diff defaults
Changed the cvd to use elastics search format for package and package group filters
Made some mods as suggested in PR 1826
Forgot to move a method used by generate_clause method
Added severity params to errata
Made the publish handle empty package rules
Made the publish handle empty errata ids in rules
Fixed a couple of unit tests to aid with the publish process
Fixed some parens issues