ansible-freeipa roles do not work with Ansible 2.8 anymore, so the
minimum supported version is changed to 2.15, the oldest supported
Ansible version as of today.
Currently, the minimum supported Ansible version is 2.13, and
ansible-freeipa roles does not work with any version less than 2.9,
altough ansible-freeipa documentation states that the minimum version to
use is 2.8.
This patch fixes documentation and roles metadata to require that the
minimum Ansible version used is 2.13.
With ansible 2.3.1 it is possible to have one place as an additional utils
module to do all the needed steps to be able to generate the environment for
new and older ipa versions.
The library modules are now a lot smaller.
The minimal ansible version has been increased to 2.3.1.
In the future it might now also be possible to have a special
ansible_ipa_client version for ipa < 4.4 in this utils module.
