Flights, Pilots, Search and more

In this series of commits I have:
* added airline logos (from old vataware)
* added country flags
* created flights index page showing currently active flights
* created flight detail page (with placeholder for map and route points)
* created pilots index page with statistics on number of flights (default sort), miles flown and time in time
* created pilot detail page with statistics, current and previous flights
* implemented a simple search for flights (by callsign) and pilots (vatsim ID and name)
* hid the top nav bar and a couple of links from the main nav bar
* updated a couple of migration files
* made some layout/visual modifications

Also, big improvements have been made to the data fetcher
* Arrival detection (proximity to airport, altitude and speed)
* Update arrival time on arrival
* Remove 'missing' flights when inactive for an hour (unless it passes the arrival detection)

It's very well possible there are still a number of bugs, I have tried to test as extensively as possible but I can't keep keep my laptop running all the time for cron to fetch new flights.