better messaging on handling of unknown functions. fixes #606

docs/scarpet/api/Auxiliary.md

@@ -444,6 +444,9 @@ algorithm has taken in to account last time mobs spawned.
 Schedules a user defined function to run with a specified `delay` ticks of delay. Scheduled functions run at the end 
 of the tick, and they will run in order they were scheduled.
 
+In case you want to schedule a function that is not defined in your module, please read the tips on
+ "Passing function references to other modules of your application" section in the `call(...)` section.
+
 ### `statistic(player, category, entry)`
 
 Queries in-game statistics for certain values. Categories include:

docs/scarpet/api/Entities.md

@@ -746,6 +746,10 @@ Required arguments: `entity, amount, source, attacking_entity`
 It doesn't mean that all entity types will have a chance to execute a given event, but entities will not error 
 when you attach an inapplicable event to it.
 
+In case you want to pass an event handler that is not defined in your module, please read the tips on
+ "Passing function references to other modules of your application" section in the `call(...)` section.
+
+
 ### `entity_load_handler(descriptor / descriptors, function)`, `entity_load_handler(descriptor / descriptors, call_name, ... args?)`
 
 Attaches a callback to when any entity matching the following type / types is loaded in the game, allowing to grab a handle

docs/scarpet/api/Events.md

@@ -263,6 +263,10 @@ handle_event('tick', _() -> foo('tick happened')); // built-in event
 handle_event('tick', null)  // nah, ima good, kthxbai
 </pre>
 
+In case you want to pass an event handler that is not defined in your module, please read the tips on
+ "Passing function references to other modules of your application" section in the `call(...)` section.
+
+
 ### `signal_event(event, target_player?, ... args?)`
 
 Fires a specific event. If the event does not exist (only `handle_event` creates missing new events), or provided argument list