Pull code to handle modeled events into a function

[kylebaron]

Summary

DEVTRAN is a huge function doing a lot of stuff. I'm going to start a series of PRs where we pull some of this code into a function.

For now, I'm going to pass everything we need in; I think down the road, I'll look to create some objects that can organize the data a little better.

This PR pulls code related to handling modeled events into a new file.