Override less Ansible settings (#224)

* Do not escalate privileges by default

* Do not disable host key checking by default

* Do not mute deprecation warnings by default

* Provide ansible.cfg only as an example

The new example file does ONLY contain options that are related to this
playbook.

* Remove explicit inventory path from scripts

The inventory file is specified in ansible.cfg, see README.md.

ansible.example.cfg

@@ -0,0 +1,2 @@
+[defaults]
+inventory = inventory/my-cluster/hosts.ini  ; Adapt this to the path to your inventory file