remove dependencies on dojo/aspect
remove dependencies on dojo/dom.isDescendant()
Name variable "node" rather than "widget" since children can be plain DOM nodes too.
Also simplify code in removeChild().
Remove dialogId property; can just use id.
Also, change class name from duiDialogUnderlay to d-dialog-underlay.
Massive cleanup of API comments and conversion to JSDoc.
always use dojo/domReady! as a plugin, rather than a function that takes a callback