Now using get_superevent_by_date_id_or_404 to retrieve the superevent
for log creation via the web interface.

Created a web form and API resource for confirming a superevent as
a GW.  Also added and utilized permissions for allowing this action.

Remove commented out code blocks for file handling in
superevents/forms.py.

return 10 superevents by default for superevents list resource, instead of 3.  Matches behavior of events list resource.

fixing issue with writing event logs when a preferred event is added to a superevent which previously didn't have a preferred event