refs #341; fixed a bug, that caused the participant export to throw an
exception for tours with more than 9 participants
fixes #341; restores the original sac_logo.png file; the new header logo
now only shows up in the page layout
fixes #342; corrects a small typing error
fixes #343; fixed start date filter not working with range filter "current"
fixes #337; tours marked as not carried out in the future now have an icon