Fix problem with Toke Of Siegfried and Improve Unique IDs system

Extended item_check to also add unique_ids to any non-stackable items that lack it
- This is useful in case an old server that didn't have the unique_id feature enabled is updated to the latest version.
- It'll only have effect if item_check is enabled in the configuration files.
Fixed an issue when Token_Of_Siegfried is used, under certain conditions
- If the Token_Of_Siegfried is the first item in inventory, it would not get detected and consumed correctly.