fix #1520
When the layout was locked, the viewers still could move or resize each window just once, before the windows get locked. The problem was conceptual, since the properties draggable and resizable have been added to the layout definition, creating a conflict between the definition of the layout (draggable/resizable) and the role definition in addition to the locked state.
Merge pull request #173 from fcecagno/fix1520

fix #1520