Fixes #16847.  Add border-collapse css to work around jsfiddle css overrides.
Like !ComboBox, add labelType property to Tree (well actually, to dijit/tree/ObjectStoreModel) to allow the label to be HTML.  Fixes #16901 !strict.
Clarify API comments for type of "label" an "title" properties to show they are interpreted as HTML. Refs #16901 !strict.
Add Dialog.closable property, to hide the [x] icon and disable ESC as a way to close the dialog.  Also removing aria-describedby property, as this is handled implicitly by _WidgetBase.  Fixes #8345 !strict.