Screens (composites, controls, shells, ...) are filled/composed
by using one of several predefined panes.
Panes are created by using the central pane factory class.
The following coding creates the screen shown below.
Complete container (including user area) is composed within the following steps:
1. calls method preInitContainer(IGridLayoutPane parentPane)
2. calls method prepareContainer(IGridLayoutPane parentPane)
3. create and initialize user area
4. calls method postInitContainer(IGridLayoutPane parentPane)
Can only be called one time.