Heavy handed fix to keep Amarok from crashing when resizing the ContextView.

The issue basically comes down to the fact that a LayoutItem can only have one child layout, and any layouts that are added beyound the first causes the previously added one to be deleted.

This in turn casused the pointers in the list of layouts kept by ContextLayout to become invalid (The last entry is always valid though...)

So for now, copletely disable support for multiple collumns.