Ensured that CAPIData objects are JSON Serialisable

While it isnt directly an issue in main (right now), the fix applies
here forward, so we may as well do it here and not deal with a headache
later.

EDMarketConnector.py

@@ -1216,14 +1216,11 @@ class AppWindow(object):
             )
             if f:
                 with open(f, 'wb') as h:
-                    h.write(json.dumps(
-                        data,
-                        ensure_ascii=False,
-                        indent=2,
-                        sort_keys=True,
-                        separators=(',', ': ')).encode('utf-8')
-                    )
-
+                    h.write(json.dumps(dict(data),
+                                       ensure_ascii=False,
+                                       indent=2,
+                                       sort_keys=True,
+                                       separators=(',', ': ')).encode('utf-8'))
         except companion.ServerError as e:
             self.status['text'] = str(e)