Switch to json encoded meta data

Instead of parsing a comma separated list of photo urls, we retrieve a
json array of meta data (url, title, size).

list

@@ -1 +1,31 @@
-1.jpeg,2.jpeg,3.jpeg,4.jpeg
+[
+  {
+    "url": "1.jpeg",
+    "size": 36,
+    "title": "Beachside"
+  },
+  {
+    "url": "2.jpeg",
+    "size": 19,
+    "title": "Epica, live at the Agora"
+  },
+  {
+    "url": "3.jpeg",
+    "size": 41
+  },
+  {
+    "url": "4.jpeg",
+    "size": 41,
+    "title": "City Museum"
+  },
+  {
+    "url": "5.jpeg",
+    "size": 25,
+    "title": null
+  },
+  {
+    "url": "6.jpeg",
+    "size": 37,
+    "title": "Boat in Glass"
+  }
+]