Refactor Event building structure

Context

Each type of data file should return the entire Event so that the trigger time can be saved to the event, not the channels.

Summary

• New constructor added for Event to set channels, trigger time and id
• getNextChannels() is now getNextEvent() and returns the entire event
• The ID for each event is set in the constructor instead of being incremented in the run manager using incrementID()
• The trigger time from the event is now passed into the writers' push method to be used while writing
• I also updated the formatting of some comments that weren't showing up in doxygen

How was this tested?

Compiled and ran trying all 3 file types using vanwftk and the event stepper.