By kiam: Added the code to allow third-party modules to indicate to the module where to look for the highlighter recipes; re-arranged the code.
By kiam: added the code to handle the CSS files, to allow third-party modules to alter the path to the plugin (and change it to an external URL); removed some JavaScript settings not anymore used.
By kiam: Changed the name of a public function.
By kiam: Removed the reference to the undefined PHP variable; re-arranged the code.