Update the mediaQuery3ColumnApp

Update the mediaQuery3ColumnApp, cleanup the header html and the views js as well.  I also changed the way the layotu transitioned so that now for Medium the right column is hidden and the left and center columns are shown (navLeft | mainCenter) or (navLeft | lastCenter) instead of (mainLeft | lastCenter). I think it is more common to have the left nav stay fixed instead of having it transition