Add consistency to events that are associated with secondary JSON files

[barrywimlett]

Handle the journal event telling us that a new navroute has been written to NavRoute.json

Ideally internally consume the journalevent and then parse the json file and trhow/fire a new event based on the contents.

[barrywimlett]

I've renamed the issue there are several events which nowhave associated secondary json files NavRoute,Shipyard,ModuleInfo,Cargo and MarketData.

I have added internal event handlers for these events on the journalWatcher which for 'live' events will read the secondary json file and then raise another event with the full data. I have also added a series of public methods to the journalWatcher to allow access to the secondary json data.

I found the additional methods added to the MarketData event only after I was almost done, I have left them in place. However I personally feel that the Event/EventArgs classes should where possible remain data/property only. So I have not extended the other events likewise.

[barrywimlett]

This issue should be associated with PullRequest#21