New server management module

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

    plugins/modules/ipaserver.py

The server module allows to ensure presence and absence of servers. The
module requires an existing server, the deployment of a new server can
not be done with the module.

DNSName has been added to ansible_freeipa_module in plugins/module_utils
as this is used for locations.

Here is the documentation for the module:

    README-server.md

New example playbooks have been added:

    playbooks/server/server-absent-continue.yml
    playbooks/server/server-absent-force.yml
    playbooks/server/server-absent-ignore_last_of_role.yml
    playbooks/server/server-absent-ignore_topology_disconnect.yml
    playbooks/server/server-absent.yml
    playbooks/server/server-hidden.yml
    playbooks/server/server-location.yml
    playbooks/server/server-no-location.yml
    playbooks/server/server-no-service-weight.yml
    playbooks/server/server-not-hidden.yml
    playbooks/server/server-present.yml
    playbooks/server/server-service-weight.yml

New tests for the module:

    tests/server/test_server.yml

Change in module_utils/ansible_freeipa_module:

    DNSName is imported from ipapython.dnsutil and also added to __all__