[jdom-interest] update setAttribute(...) JavaDoc

[Jason Hunter]

The docs online say: "This sets an attribute value for this element. Any
existing attribute with the same name and namespace URI is removed." 
How much clearer can you make it?

-jh-

> Could someone update the JavaDocs for setAttribute(
) to tell a developer that actually reads them (yes some really
> do ;-) ) that a set will do an implicate ‘add’ if the Attribute does not already exits for the Element?  I have a RC
> 8 copy of the JavaDocs and this is not as clear as it should be, IMHO.  The only way I found this out is my reading
> the mailing list.