A better name for event's customer list export#1069

Hi.
When exporting the customers list of a event, the file is always named event.csv

If one have multiple events to export, we got X files named event.csv which can be very confusing (which event is that even.csv files ?).

It would be great to have that even.csv named for example with the event’s title.

So the file should be a_big_fiesta.csv, another one opening.csv, etc etc

Thx