Code cleanup and consolidation

[Bleyddyn]

Just recording these here so I don't forget. I'm not even sure all of these make sense, they all need to be researched more.

• Combine elements of METConquerableStations and METIDtoName into a super-class.
• Create a super-class for all of the detail windows (e.g. ShipDetailsWIndowController, ModuleDetailsWindowController) with as much common code as possible.
• Combine XmlFetcher and XmlDownloadOperation (or replace use of one with the other).
• Can GenericDownloadOperation be replaced with NSURLDownload?
• Map out all App and Database update checking code and make sure it all makes sense.
  Big question: If the App's hard coded database version is e.g. 18, and the local database is 18, will the app still check for a more recent version and download it, if it finds one?