New-look event form

Our forms for adding events and updating events are now easier to use - I have added a date picker to the date field, so a little calendar pops up when you click into the date field (or click on the calendar button next to it), and allows you to select the date of your event.

I also looked at time pickers, but these were generally hard to use and slower than entering the time in the format that we currently have.

I hope that people will now find it easier to add and edit their events.