[FIX] #609 Cropped text on several wizard pages

Removed the fixed sizes for all wizards. This should ensure
that all contents in a wizard are visible. Fixed also
a minor bug in the ConfigurationSettingsWizardPage that "blow up"
the size of the SarosConfigurationWizard.

Change-Id: I248d4128665f8b530bc755f89a9cf6fc36482be5
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/984
Tested-by: Jenkins CI
Reviewed-by: Christoph Krüger <christoph.krueger@fu-berlin.de>
Reviewed-by: Conrad Läßig <conrad.laessig@gmail.com>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>