Editor: dijit._getTabNavigable() not finding editor content area

[bill]

dijit._getTabNavigable() won't find the content part of an editor. It does find the toolbar. This means (among other things) that if there's an editor in a Dialog, shift-tab (when past the end of the dialog) will skip over the editor content area and go right to the toolbar.

It's also causing issues re [19948] where dijit doesn't realize that the editor has gotten focus.

[bill]

(In [19955]) Make isTabNavigable() return true for editor iframes. It's pretty messy detecting which iframes are editors, wish there was a better way. Fixes #9766, refs #9735 !strict.

[bill]

PS: I could of course check if there's an editor widget connected to the iframe, using getEnclosingWidget() or maybe the iframe's id, but I was trying to write general code that would detect any navigable iframes. Not sure if I was successful or not.

[liucougar]

(In [19965]) refs #9766: correctly handle contentEditable elements (they should be considered as focusable) also refs #9735 also fixed some strict warnings