Allow overrides to fillFaceboxFrom* behavior via $.facebox.fillFrom*

[Empact]

Improve customizability by moving the private fillFaceboxFrom* functions onto the $.facebox object as $.facebox.fillFrom*. E.g., you can now override $.facebox.fillFromAjax to customize your AJAX calls.

Previously private function which are now available on $.facebox: init, fillFromAjax, fillFromImage, fillFromHref

Previously private functions which remain private: As inner functions: showOverlay, getPageHeight, getPageScroll, makeCompatible As local to the closure: hideOverlay

In $.facebox, I pass the full first data argument to the fillFrom* functions, to allow people to use and process additional arguments on the call side as well.

This addresses pull request #26 and #11 by given people the hooks they need to customize behavior to suit their apps.