Get variables from inventory root for "all" group
Get variables from inventory root for "all" group

* Ansible normally has an "group_vars/all" but this does not really
exist in AWX / Ansible Tower, but vars are set on the inventory "root"
instead
* Implement get_inventory_vars function to fetch vars from inventory
* Add all hosts to "fake" group "__inventory_all__"
* Add inventory vars to group "__inventory_all__"

stigchristian/ansible-tower-inventory