Changes to EventsList pages.

Fixes #453 by checking if event.start_date is set before attempting to access it.
Allows displaying events from the past without start_dates by grouping them into a weekless events bucket.
Removes upcoming events from Event pages to make it a little bit simpler and the homepage always has them.

Tested by deleting the start_time from 2010ct and ensuring that the Event List loaded, displaying that event at the bottom.