fixes #6439 / BZ 1094190 - Include notification on add/remove pkg filter rule

When the user adds/removes a rule from a package filter (associated
with a content view), display a notification consistent with what
is done for package groups.
Merge pull request #4367 from bbuckingham/issue-6439

fixes #6439 / BZ 1094190 - Include notification on add/remove pkg filter rule