Fuel Voxel Damage

issue #372 
depends on / includes #423 
* Introduces destructionDamage for voxels
* FuelVoxel spawns an additional Explosion
* Fix models to colorcode cockpit and fuelvoxels (missed in the modelPR)
* remove zox models instead of trying to keep them in sync
* Add FrozenGameScenario (F3) to better test hitting special voxels
* Rockets can be fired at nothing, thought we agreed on that