LPS-32830 rename callback as eventName

Hey Brian, in this new pattern this variable is not a callback anymore but an eventName. I think we should keep the names different because otherwise users will understand that a callback is a function called back whereas an event is something you have to listen to.

We are going to apply this new patter to all the select_xxx.jsp next week. This was just the prototype to see if Nate and you liked it.

thanks!