Added optional id for creation of TitlePane and Floating Widgets.

This id allows styling the individual widgets using CSS to add an icon on the TitleBar, for example:

    #sidebar_Print .dijitTitlePaneTextNode {
        background-image: url('../js/gis/dijit/Print/images/print.png');
        background-repeat: no-repeat;
        background-position: 0px 2px;
        padding-left: 21px;
    }

This can also be used to interact with the widgets using code via the widgetid and id attributes.