Prepare for Image iteration.

Though there's no code in the official CEGUI which exposes this through
Lua yet.
Fix broken event binding.
Use more correct ToggleButton type name.

"Checkbox" is deprecated.
Don't put script refences in the layout.

All bindings should happen in code, so as not to tangle.
Fixed incorrect method call.

Since upgrading CEGUI.
Wrap lines in hover help.