* Make sure about window background covers entire window
* Make sure start center images are centred

Change-Id: I402448ef4ea77633fe4e1ad5d5f93952efb495af
Reviewed-on: https://gerrit.libreoffice.org/4308Reviewed-by: Thorsten Behrens <tbehrens@suse.com>
Tested-by: Thorsten Behrens <tbehrens@suse.com>