make the etherpad content templated

[mrjoshuap]

Add a nicer snippet and generate the user numbers correctly.

I mostly want an easier way to make adjustments for other workshops...

I ran a few tests, but did not provision with it.

etherpad-user_count_7.txt etherpad-user_count_13.txt etherpad-user_count_103.txt

[jorgemoralespou]

Thanks for this nice addition.