Creates a draggable system of docking elements, grouped into columns.
Creates a dock inside div with numColumn columns.
Adds a new window to dock, resp. to its column with index colIndex. This window contains content. Object options may contain:
var content = OAT.Dom.create("div");
content.innerHTML = "lorem ipsum :)"
var d = new OAT.Dock("parentDiv", 3);
d.addObject(0, content, {title:"Sample window"});