Improve culture signs

- closes #1

culture.json

@@ -29,15 +29,15 @@
         "markerSign": "{{ const[value] }}"
     },
     "const": {
-        "arts_centre": "",
+        "arts_centre": "🎨",
         "cinema": "🎦",
         "community_centre": "",
         "fountain": "⛲",
         "studio": "",
-        "theatre": "",
-        "artwork": "",
+        "theatre": "🎭",
+        "artwork": "🎨 ",
         "gallery": "🖼",
-        "museum": "",
+        "museum": "🏛 ",
         "theme_park": ""
     }
 }

tourism_attractions.json

@@ -27,7 +27,7 @@
     },
     "const": {
         "aquarium": "🐟",
-        "artwork": "🛌",
+        "artwork": "🎨 ",
         "attraction": "",
         "gallery": "🖼",
         "museum": "",