Squish: Make sure correct output panes are used

We expect the first five toggle buttons for output panes to be visible
by default. Additionally added buttons will have the property 'occurrences'
with a value depending on their position - not their label. Using the menubar
for these additional output panes is safer.

Change-Id: Ie58f8dd56ec35bfa9f6bba871aa807e4b1507c75
Reviewed-by: Robert Loehning <robert.loehning@digia.com>