Snippet019TreeViewerWithListFactory

I think the layout call on the shell after opening it is unnecessary.
The open() calls calls already updateLayout via the following call
chain:

GridLayout.layout(Composite, boolean) line: 200
Shell(Composite).updateLayout(boolean) line: 1812
Shell.setVisible(boolean) line: 2813
Shell.open() line: 1923

Where are more such examples, I post changes for them after Jens had the
chance to look at this one.

Change-Id: Ib6fc53cf88ea181963788ef913da38fe7e82349d
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>