group

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>