Handle possible invalid ModConfig configuration value.

Fix thread problems when loading a save without this mod.

Support Below and Beyond

Fix icons.

Gagarin update/ModConfig Rebord compatibility

Fix handler thread piling up on reloading a save and potentially causing peformance problems.

Remove battery related logic as the Sagan update has removed batteries from rovers entirely.

Fix crash due to missing tunnel-zone information during game loading.

Do not build the zone map for the "New Game" screen as it is not a real game map.

Fix ModConfig compatibility/usage.