New pwpolicy management module

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

  plugins/modules/ipapwpolicy.py

The pwpolicy module allows to ensure presence and absence of pwpolicies for
groups.

Here is the documentation for the module:

  README-pwpolicy.md

New example playbooks have been added:

  playbooks/pwpolicy/pwpolicy_absent.yml
  playbooks/pwpolicy/pwpolicy_present.yml

New tests added for pwpolicy:

  tests/pwpolicy/test_pwpolicy.yml