Changed headless_pianobar to support command-line arguments and reading the pianobar config file

The script supports command-line arguments to control pianobar. ex: "headless_pianobar p" starts pianobar (assuming default key bindings). The idea is that someone could just set a bunch of key bindings. It will also parse the pianobar config file so that it can intelligently read the keys.

I know last time you said that it might make sense to keep development in another project, and I am ok with doing that, but I, personally, would rather keep it here because it should make it into my distro's official packages, and it really is the same script. I do not anticipate making more changes to it, unless if someone uncovers a bug, or you change how pianobar functions. The only other change I see being made is to make it more portable, as the original author pointed out, but if it happens, I probably won't do it.