Documentation

Updated the documentation with what I figured out during my trial run. I'll be keen to know whether my understanding of how things work reflect reality :-)
The event backend should be running while loading the database.  Either:

* Run the main.js in the top-level directory to run the event backend as well as the full catalog frontend
* Run modules/events/main.js to just run the event backend without the frontend.

If a smaller amount of records have been loaded, the event backend can safely be kicked off after the load to catch up.  The event log is used by the next step to populate the search module.