Add the author of an event as an organizer by default, refs #383

Also cleaned up the Event model a bit, but it still has a lot of things that
can be removed.
Show more information in events/show, refs #383

Show the date the event ends and make it look better when some of the attributes
of the event are not set.
Add options to toggle repository and remove the space in spaces/edit
Better definitions of what is mandatory in setup_conf.yml, refs #781

Several things are actually mandatory, if they are not in setup_conf.yml the
application will crash in some places. More information about it will be added
in the docs.