Lightbox global object

Man this makes so much more sense.

**There is now one global Lightbox object.**

This makes for a much simpler (and redesigned) method interface:
- **get** (controller, action, get, post, callback)
- **getByUrl** (url, post, callback)
- **addFormHandler** (name, function) - full handling of submission for manual/custom ajax calls (see login and cart), *must return false*.
- **addFormCallback** (name, function) - function to run the response from the automatic form ajax submission.
- **addOpenAction** (function) - function to run when the lightbox loads.
- **addCloseAction** (function) - function to run after lightbox closes.
- **changeContent** (html)
- **close** ()
- **confirm** (message) - replace content with formatted message and close button.
- **displayError** (message) - Adds an error message to the top of the current lightbox.

There's other useful methods, but I'll detail them in a write up elsewhere.