Review config file load order, location support

[deoren]

I was watching an Ansible training video earlier today and saw this list of supported paths for the Ansible configuration file:

• Ansible_Config environment variable
• ansible.cfg file in current directory
• .ansible.cfg file in user's home directory
• /etc/ansible/ansible.cfg default settings file

I've not researched whether the files are merged with settings in one overriding settings in others or if just one file is used. For our purposes, just going with one file is probably sufficient.

Without looking at the code, I think we're already handling points 2 and 4, shouldn't be too hard to add support for the others.