Cleaned up countitem-type script commands (#3657)

* Fixes #3612.
* Separated the countitem-type script commands into their own functions.
* Created a global count function to be used between them.
Thanks to @kisuka, @Normynator and @Atemo!

doc/script_commands.txt

@@ -4941,8 +4941,8 @@ If player is not in a guild or storage is open, 'guildstoragedelitem2' will retu
 
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-*countitem(<item id>)
-*countitem("<item name>")
+*countitem(<item id>{,<accountID>})
+*countitem("<item name>"{,<accountID>})
 
 This function will return the number of items for the specified item ID that the
 invoking character has in the inventory.
@@ -4978,10 +4978,10 @@ If player is not in a guild or storage is open, 'guildstoragecountitem' will ret
 
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-*countitem2(<item id>,<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>)
-*countitem2("<item name>",<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>)
-*countitem3(<item id>,<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>,<RandomIDArray>,<RandomValueArray>,<RandomParamArray>)
-*countitem3("<item name>",<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>,<RandomIDArray>,<RandomValueArray>,<RandomParamArray>)
+*countitem2(<item id>,<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>{,<accountID>})
+*countitem2("<item name>",<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>{,<accountID>})
+*countitem3(<item id>,<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>,<RandomIDArray>,<RandomValueArray>,<RandomParamArray>{,<accountID>})
+*countitem3("<item name>",<identify>,<refine>,<attribute>,<card1>,<card2>,<card3>,<card4>,<RandomIDArray>,<RandomValueArray>,<RandomParamArray>{,<accountID>})
 
 Expanded version of 'countitem' function, used for created/carded/forged items.