add new spawn system
add debuging code for new spawn system
add documentation for the new spawn system
add map extra spawn group definition in json
don't need to check for existing item in map, is automatically created (and empty)
Use automatically deducted item group for death drops.

If the group exists, use it to create a item list and add those items to the map, skipping the old item drops.
move zombie cop drops to json
move swimmer zombie drops to json
move zombie scientist drops to json
Merge new item spawn system.