Update events-from-CSV code

Get it more like what's on the Hassle website right now (update the
template); and re-write code for filtering what is shown (filter data
then render template)

ALL SORTING CODE removed - @mathtest you'll need to help me work on
that. i.e. I was about to move forward but decided that either (a)
people can filter and sort in the SPREADSHEET, and/or (b) people can use
real date objects in the spreadsheet, so that we can more or less create
date objects in JS land from the Date Strings