Slide transitions in a tablet view now slide across the left pane.

[edchat]

Prior to the Layout updates Slide transitions in a tablet view would not slide across the left pane because the Layout controller would set the zIndex for the nodes other than the one in the Center higher than the one in the center, but the code setting the zIndex was removed.

Now transitions can occur in any of the regions, so we should see if we can get some type of default behavior which works well, and provide a way for the app developer to be able to override the default behavior as well.