Complete social share campaign with a single share

Social share campaigns are now marked as completed for a member after they share on one channel.

This means the campaign will disappear from the "To-do"-based tabs after the first share, preventing them from clogging up those tabs for users that don't share on all channels.

Users can, of course, still share on multiple channels when they still have the campaign open, or they can go back to the campaign later by going to the "All" tab.