Core: implement start_inventory_from_pool (#1170)

* Core: implement start_inventory_from_pool

* Factorio/LttP/Subnautica: add start_inventory_from_pool Option

Options.py

@@ -897,6 +897,13 @@ class StartInventory(ItemDict):
     display_name = "Start Inventory"
 
 
+class StartInventoryPool(StartInventory):
+    """Start with these items and don't place them in the world.
+    The game decides what the replacement items will be."""
+    verify_item_name = True
+    display_name = "Start Inventory from Pool"
+
+
 class StartHints(ItemSet):
     """Start with these item's locations prefilled into the !hint command."""
     display_name = "Start Hints"