Tracking: Decreased default SkyLines tracking interval to 5 sec
TrackingConfigPanel: Use exponential list of tracking intervals

Offering "17 min, 35 sec" doesn't really make sense, but allowing intervals
below "5 sec" can make sense for some users.
Waypoints: fix coding style
Waypoints: use nullptr instead of NULL
Waypoints: delete copy constructor, replacing NonCopyable
Airspaces: delete copy constructor, replacing NonCopyable