[RFE] Allow multiple groups creation.

Adding an option `groups` to create multiple groups in one operation.
Adding tests (present/absent/external/nonposix) with server and
client context.
Simple example of `groups` option:
```
tasks:
- name: Ensure 2 groups are present
  ipagroup:
    ipaadmin_password: SomeADMINpassword
    groups:
    - name: group1
    - name: group2
```

Signed-off-by: Denis Karpelevich <dkarpele@redhat.com>

playbooks/group/add-group.yml

@@ -0,0 +1,23 @@
+---
+- name: Playbook to handle groups
+  hosts: ipaserver
+  become: true
+
+  tasks:
+  - name: Create group ops with gid 1234
+    ipagroup:
+      ipaadmin_password: SomeADMINpassword
+      name: ops
+      gidnumber: 1234
+
+  - name: Create group sysops
+    ipagroup:
+      ipaadmin_password: SomeADMINpassword
+      name: sysops
+      user:
+      - pinky
+
+  - name: Create group appops
+    ipagroup:
+      ipaadmin_password: SomeADMINpassword
+      name: appops