Implement CSV / TSV import (#45)

- add csv/tsv importer
- add `make_map` script function
- add `alt name` field property
- add `construction script` field property
- add `construction script` game property

doc/function/index.txt

@@ -11,6 +11,7 @@ These functions are built into the program, other [[type:function]]s can be defi
 | [[fun:to_color]]		Convert any value to a [[type:color]]
 | [[fun:to_image]]		Convert any value to an [[type:image]]
 | [[fun:to_date]]		Convert any value to a [[type:date]]
+| [[fun:make_map]]		Create a [[type:map]] from two [[type:list]]s
 | [[fun:type_name]]		Get the type of a value
 	
 ! Numbers			<<<

doc/function/make_map.txt

@@ -0,0 +1,17 @@
+Function: make_map
+
+--Usage--
+> make_map(keys: some_list, values: some_list)
+
+Creates a new map. Converts the elements in keys to strings, and uses them as keys for the elements in values.
+
+Produces a warning if keys and values are not of the same size.
+nil keys will be ignored.
+
+--Parameters--
+! Parameter	Type				Description
+| @keys@	[[type:list]]		List of keys.
+| @values@	[[type:list]]		List of values.
+
+--Examples--
+> make_map(keys:["apple", "durian", 3], values:["good", "bad", "not edible"]) == ["apple":"good", "durian":"bad", "3":"not edible"]