New group management module

There is a new group management module placed in the plugins folder:

  plugins/modules/ipagroup.py

The group module allows to add, remove, enable, disable, unlock und undelete
groups.

The group module is as compatible as possible to the Ansible upstream
`ipa_group` module, but addtionally offers to add users to a group and also
to remove users from a group.

Here is the documentation for the module:

  README-group.md

New example playbooks have been added:

  playbooks/user/add-groups-to-group.yml
  playbooks/user/add-user-to-group.yml
  playbooks/user/add-group.yml
  playbooks/user/delete-group.yml

playbooks/user/add-user-to-group.yml

@@ -0,0 +1,13 @@
+---
+- name: Playbook to handle groups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  # Add user member brain to group sysops
+  - ipagroup:
+      ipaadmin_password: MyPassword123
+      name: sysops
+      action: member
+      user:
+      - brain