Remove CrateDrop and move all crate spawning logic into CrateSpawner
Add support for multiple crate actors to be spawned from CrateSpawner
CrateSpawner - combine DeliverByAircraft and DeliveryAircraft properties
Replaced references of CrateDrop with CrateSpawner in RA maps
Fix style issues in CrateSpawner / convert altitude to world coords
Use add and remove world notifications on Crate to maintain the CrateSpawner list of crates
Merge pull request #4360 from cjshmyr/crates

CrateSpawner changes