reworked the layout so that center may be positioned anywhere in the DOM.  Fixes #4667.  However, I don't think this addresses "goofy" spiral layouts, which I don't plan to support in BorderContainer post 1.0, so we may need an exception for that.
reworked the layout so that center may be positioned anywhere in the DOM.  Fixes #4667.  However, I don't think this addresses "goofy" spiral layouts, which I don't plan to support in BorderContainer post 1.0, so we may need an exception for that.

git-svn-id: 674a2d6b1e32e53f607eb824547723f32280967e@10757 560b804f-0ae3-0310-86f3-f6aa0a117693

redaktor/deliteful