Load time duration from string (containing units)

Allows to load from a string like "2d 4h" meaning "2 days and 4 hours".

data/json/items/biosignatures.json

@@ -5,7 +5,7 @@
     "name": "bird litter",
     "weight": 40,
     "color": "brown",
-    "spoils_in": 112,
+    "spoils_in": "4 days 16 hours",
     "comestible_type": "FOOD",
     "symbol": "%",
     "quench": -3,

data/json/items/chemicals_and_resources.json

@@ -771,7 +771,7 @@
     "name": "hickory nuts",
     "name_plural": "hickory nuts",
     "description": "A handful of hard nuts from a hickory tree, still in their shell.",
-    "spoils_in": 4320,
+    "spoils_in": "180 days",
     "price": 0,
     "weight": 212,
     "volume": 1,
@@ -785,7 +785,7 @@
     "name": "pecan",
     "name_plural": "pecans",
     "description": "A handful of hard nuts from a pecan tree, still in their shell.",
-    "spoils_in": 4320,
+    "spoils_in": "180 days",
     "price": 0,
     "weight": 212,
     "volume": 1,
@@ -799,7 +799,7 @@
     "name": "pistachio",
     "name_plural": "pistachio",
     "description": "A handful of hard nuts from a pistachio tree, still in their shell.",
-    "spoils_in": 2160,
+    "spoils_in": "90 days",
     "price": 0,
     "weight": 180,
     "volume": 1,
@@ -813,7 +813,7 @@
     "name": "almond",
     "name_plural": "almond",
     "description": "A handful of hard nuts from a almond tree, still in their shell.",
-    "spoils_in": 7200,
+    "spoils_in": "300 days",
     "price": 0,
     "weight": 212,
     "volume": 1,
@@ -827,7 +827,7 @@
     "name": "peanut",
     "name_plural": "peanuts",
     "description": "A handful of hard nuts from a peanut bush, still in their shell.",
-    "spoils_in": 5760,
+    "spoils_in": "240 days",
     "price": 0,
     "weight": 200,
     "volume": 1,
@@ -841,7 +841,7 @@
     "name": "hazelnut",
     "name_plural": "hazelnuts",
     "description": "A handful of hard nuts from a hazelnut tree, still in their shell.",
-    "spoils_in": 3600,
+    "spoils_in": "150 days",
     "price": 0,
     "weight": 212,
     "volume": 1,
@@ -855,7 +855,7 @@
     "name": "chestnut",
     "name_plural": "chestnuts",
     "description": "A handful of hard nuts from a chestnut tree, still in their shell.",
-    "spoils_in": 4320,
+    "spoils_in": "180 days",
     "price": 0,
     "weight": 240,
     "volume": 1,
@@ -869,7 +869,7 @@
     "name": "walnut",
     "name_plural": "walnuts",
     "description": "A handful of hard nuts from a walnut tree, still in their shell.",
-    "spoils_in": 4320,
+    "spoils_in": "180 days",
     "price": 0,
     "weight": 240,
     "volume": 1,