turnkey-init-firstlogin => turnkey-init-fence

rational: don't name the component after a subcomponent. Calling it
init-firstlogin confuses what this script is supposed to do. The firstlogin is
just one part of the fence mechanism. The other part is the turnkey-init-fence
service. They work together and one deactivates the other.
deleted docs/README, created README.rst
updated README.rst