Added support for some Nagios 3 directives.

Removed any Emacs lisp commands that I don't understand.
Rewrote some of the syntax highlighting so that comments and multi-word directives are handled properly.
Removed some unnecessary code.
Removed the "apropos.el" requirement. I don't think it's used anywhere.
Lowercased the all-caps comments.
Added the GPL3/Copyright notice to the top.
Changed the comment face so that they're highlighted by default.