Combat for buildings

[domob1812]

Buildings should be able to "take part" in combat, just like vehicles. They will have HP (shield / armour) and may as well have attacks (for turrets at least). We can use the centre coordinate for target distance purposes.

When a building is destroyed, then all characters in them + the vehicles they are in will just die / be destroyed. All inventory items (from building accounts as well as character inventories) will be combined into a single "building inventory", and then each position will have a 30% chance to drop on the floor, rather than being destroyed as well.