Make ansible config reloadable to read ansible.cfg from playbook's dir (fixes issue #5115)

This required me to move all constant initialization into function, and to avoid writing overly long lines like:

        globals()['ANSIBLE_SSH_CONTROL_PATH'] = get_config(p, 'ssh_connection', 'control_path', 'ANSIBLE_SSH_CONTROL_PATH', "%(directory)s/ansible-ssh-%%h-%%p-%%r")

I moved all options into one table for an easy overview and made a parser with some tests.