Damaged by terrain

This is a trait that replaces the PoisonedByTiberium trait for a more general approach, this now not only works on resources but also on terrain, have a unit that cant live on anything but tiberium add Clear and Beach to the Terrain variable (you might need to add Rough too but I have no idea what terrain that is).
This isn't quite right: the health is scaled by the number of footprint tiles on the bad terrain.  An actor with a 2x2 footprint on 2 rock tiles will start with 75% health.