Added dnf_group package module

This change adds the dnf_group package module that supports asserting presence
or absense of the promised group id on the system.

packages:
  "system-tools"
    policy => "present",
    package_module => dnf_group;

Note: Package marks (user, dep, group) influence the behavior of this module.
For example, once a package is installed directly it will retain the user mark
until explicitly re-marked.

Ticket: CFE-2852

Author: nickanderson