Pilotfile is saved too often within the Barracks

The barracks is rather happy about saving to the plr file. Often.

pilotfile::save_player() is naturally triggered when a new pilot is created or cloned, but it is also saved whenever switching between singleplayer and multiplayer modes, as well as the simple act of just selecting a pilot.

The pilot file should only be saved if there are changes made, or if it needs to be converted to a different version when the Accept button is pressed.