Minetest player_notes mod - API
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player_notes.add_note(name, target, note)
 Adds a note to a player
 Returns nil on success, otherwise error string
 ^ name		->	player or object which added the note
 ^ target	->	to which player the note should get added
 ^ note		->	the note text to add to <name>

player_notes.rm_note(target, key)
 Removes a note from a player
 Returns nil on success, otherwise error string
 ^ target	->	from which player the note should get removed
 ^ key		->	key of the note to remove from <name>
 
player_notes.save_data()
 Saves changed data (use this after add_note or rm_note)
 Returns nothing
 
player_notes.player[]
 player_notes.player["dummy"] = { key1 = note1, key2 = note2, ... }