Function cleanup

[ZZZank]

This PR:

• Adds type comments for most of functions in functions.js. These comments are basically copied from my functions.js
• Rewrite about half of all functions in functions.js, to make them clearer and possibly more performant. E.g. getPreferredItemInTag is rewritten to use maxOf instead of sort, this can reduce time complexity from O(n*lg(n)) to O(n), so should be faster
• fixed a horribly wrong format in unify_sawables::create_cutting(), which will prevent recipes from actually getting added
• move functions for recipe-gen from global scope to inside event callback, to prevent access
  ing by accident. Also removing an unused param event. These functions are located mostly at server_script/xxx/unification/

These changes have been applied to my fork of E6/E6E for a long time, and they seems working pretty well

[NielsPilgaard]

Thanks for the PR, I'll go over it once I find some time 😅