Patch $.ui.addContentDiv()

Allow `$.ui.addContentDiv()` to accept a pre-created DOM node as the first argument.

The bug:
This feature is suggested by the documentation as it indicates `el` may be a string or an object. However, `$.query()` only accepts a string, and no check is made to ensure that a node isn't passed. The following code will fail with "undefined is not a function" when `query` tries to strip the whitespace from the node object:

    $.ui.addContentDiv($('<div>Stuff.</div>'));

The fix:
Add more checking to ensure that the `el` and `myEl` variables are set correctly. Now `el` may be a DOM id with or without the leading `#`, an element wrapped by `$`, or a naked element. The above test case will work as advertised.