Various fixes fixes and improvements

[JoramD0]

When merged this pull request will:

• vehicleSpawner add support for post-spawn command execution .
• vehicleSpawner replace covered offroad with Theseus variant.
• vehicleSpawner add standard equipment to vehicles by default. closes #175
• Replace spawnEngineerVehicle with above mentioned vehicleSpawner changes.
• Add vehicle repair stations to engineer course and weapons handling. closes #174
• Replace airport fuel truck with Theseus variant.
• Attempt to fix stuck ATVs at airport.
• Fix floating Arcadian at driving course.

[JoramD0]

Merging now, releasing after modpack update.