Consisitency for secondary json files associated with journal events.

[barrywimlett]

This PR attempts to add some consistency to how events with secondary json files are handled.

I started this because I wanted to access the navroute.json file, however this snowballed.

Now any "live" journal event with an associated json file will cause the full json file to be read, and for a second event with the complete data from the json file to be fired.

Also consumers can now ask for a copy of each of the five json files on request.