New privilege management module

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

    plugins/modules/ipaprivilege.py

The privilege module allows to ensure presence or absence of privilege
and manage privilege permission memebers.

Here is the documentation for the module:

    README-privilege.md

New example playbooks have been added:

    playbooks/privilege/privilege-absent.yml
    playbooks/privilege/privilege-member-absent.yml
    playbooks/privilege/privilege-member-present.yml
    playbooks/privilege/privilege-present.yml

New tests for the module:

    tests/privilege/test_privilege.yml

README-privilege.md

@@ -0,0 +1,147 @@
+Privilege module
+================
+
+Description
+-----------
+
+The privilege module allows to ensure presence and absence of privileges and privilege members.
+
+Features
+--------
+
+* Privilege management
+
+
+Supported FreeIPA Versions
+--------------------------
+
+FreeIPA versions 4.4.0 and up are supported by the ipaprivilege module.
+
+
+Requirements
+------------
+
+**Controller**
+* Ansible version: 2.8+
+
+**Node**
+* Supported FreeIPA version (see above)
+
+
+Usage
+=====
+
+Example inventory file
+
+```ini
+[ipaserver]
+ipaserver.test.local
+```
+
+
+Example playbook to make sure privilege "Broad Privilege" is present:
+
+```yaml
+---
+- name: Playbook to manage IPA privilege.
+  hosts: ipaserver
+  become: yes
+
+  tasks:
+  - ipaprivilege:
+      ipaadmin_password: SomeADMINpassword
+      name: Broad Privilege
+      description: Broad Privilege
+```
+
+Example playbook to make sure privilege "Broad Privilege" member permission has multiple values:
+
+```yaml
+---
+- name: Playbook to manage IPA privilege permission member.
+  hosts: ipaserver
+  become: yes
+
+  tasks:
+  - ipaprivilege:
+      ipaadmin_password: SomeADMINpassword
+      name: Broad Privilege
+      permission:
+      - "Write IPA Configuration"
+      - "System: Write DNS Configuration"
+      - "System: Update DNS Entries"
+      action: member
+```
+
+
+Example playbook to make sure privilege "Broad Privilege" member permission 'Write IPA Configuration' is absent:
+
+
+```yaml
+---
+- name: Playbook to manage IPA privilege permission member.
+  hosts: ipaserver
+  become: yes
+
+  tasks:
+  - ipaprivilege:
+      ipaadmin_password: SomeADMINpassword
+      name: Broad Privilege
+      permission:
+      - "Write IPA Configuration"
+      action: member
+      state: absent
+```
+
+Example playbook to rename privilege "Broad Privilege" to "DNS Special Privilege":
+
+```yaml
+---
+- name: Playbook to manage IPA privilege.
+  hosts: ipaserver
+  become: yes
+
+  tasks:
+  - ipaprivilege:
+      ipaadmin_password: SomeADMINpassword
+      name: Broad Privilege
+      rename: DNS Special Privilege
+      state: renamed
+```
+
+Example playbook to make sure privilege "DNS Special Privilege" is absent:
+
+```yaml
+---
+- name: Playbook to manage IPA privilege.
+  hosts: ipaserver
+  become: yes
+  - name: Ensure privilege Broad Privilege is absent
+      ipaadmin_password: SomeADMINpassword
+      name: DNS Special Privilege
+      state: absent
+```
+
+
+Variables
+---------
+
+ipaprivilege
+------------
+
+Variable | Description | Required
+-------- | ----------- | --------
+`ipaadmin_principal` | The admin principal is a string and defaults to `admin`. | no
+`ipaadmin_password` | The admin password is a string and is required if there is no admin ticket available on the node. | no
+`name` \| `cn` | The list of privilege name strings. | yes
+`description` | Privilege description. | no
+`rename` \| `new_name` | Rename the privilege object. | no
+`permission` | Permissions to be added to the privilege. | no
+`action` | Work on privilege or member level. It can be one of `member` or `privilege` and defaults to `privilege`. | no
+`state` | The state to ensure. It can be one of `present`, `absent` or `renamed`, default: `present`. | no
+
+
+Authors
+=======
+
+Rafael Guterres Jeffman