Add init scripts and docs for Upstart and OpenRC

Expanding on @aitorpazos earlier commit of a systemd service file, here are some additional scripts and documentation updates to support Upstart and OpenRC.  Tested on Gentoo/OpenRC 0.12.4 and Ubuntu trusty/Upstart 1.12.1. 
Well, obviously you can always look up the password again in the file, but bitcoin-cli won't look in /etc[/bitcoin]/bitcoin.conf automatically (yet?).