Add translatable strings to substance field (#737)

Add translatable strings for values with usage > 1000. Left out are duplicate terms like wastewater, water waste, heat, steam.

Co-authored-by: Martin Raifer <martin@raifer.tech>

data/fields/substance.json

@@ -1,5 +1,16 @@
 {
     "key": "substance",
     "type": "combo",
-    "label": "Substance"
+    "label": "Substance",
+    "strings": {
+        "options": {
+            "fuel": "Fuel",
+            "gas": "Natural Gas",
+            "hot_water": "Hot Water",
+            "oil": "Crude Oil",
+            "rainwater": "Rainwater",
+            "sewage": "Sewage",
+            "water": "Drinking Water"
+        }
+    }
 }