[FIX] web_editor: restore snippet option data parameter

Snippet options were not receiving proper data parameter on
instantiantion due to a websitepocalypse wrong adaptation. Those
data are parameters to tweak an option behavior, directly defined
on the option's <div/> in the XML. By mistake, they were now taken
on the child <li/> element (main DOM element of the option).

A visual example of the bug is the overlay colorpicker displaying
"Background Color" as a title instead of "Overlay Color".