Add Kart::explode(id) to scriptengine

[kimden]

Sorry if it is wrong — it's pretty confusing to have several different explosions in the code, someone has to refactor all that later.

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[Alayan-stk-2]

If you think it's wrong like this and it ought to be refactored later, why not actually do that in the PR?

[kimden]

It is a bit strange to look and touch all of the items code in a 20-lines addition of one scripting function added in an hour, but sure, I'll come back to do that in one of free days